Recs.
Updated
Specs
Pros
Pro New, popular & growing
This is the most recent edition of the game and unfortunately is the only one for which official content is being produced. Do not expect to see new official adventures or splatbooks published for any of the older editions of D&D, in spite of these being vastly superior to 5e, especially in the cases of 1e and 2e.
Pro Versatile rules
While the 5th Edition rules are in a few cases simpler than those found in other D&D versions, you can still decide to change them or not play 5e at all.
Pro Free basic rules PDFs
Wizards of the Coast provides free PDFs containing the complete core mechanical rules of 5th Edition D&D (combat, exploration, spellcasting, etc.) and a selection of iconic character options, monsters, magic items, etc. drawn from the full game. Though short on variety, the basic rules are playable and accurate to the full game. Fortunately the same can also be easily found for superior, earlier versions of DnD.
Pro Almost unlimited better support materials in older systems of DnD, but hard to convert to 5e
As the most popular RPG out there, there is a huge community with lots of low quality content to share in 5e. Playing other versions of DnD you get access to amazing adventures.
Pro Bounded accuracy
Bounded accuracy is a questionable core design ideal of 5th Edition. In short, it means the numbers don't get too big; this lets weak challenges remain almost relevant for longer, and strong ones become survivable sooner. In practice, it makes the game feel very samey and it also places more focus on a character's ability to min/max and less on magical equipment than has been the case in recent editions.
Pro OGL content
As with other editions of the game, much of the content is released under the Open Game License (OGL) in principle allowing custom modification, extension and alteration of the game, though that would hardly be worth the effort, as the system is broken beyond repair. Fortunately older and superior systems of DnD exist for those not afraid to try a new system - there are massive communities for 1e and 2e.
Pro Lots of non-traditional 3rd Party Creators
The grandfather of games newest child is much more forgiving and streamlined from its origin making it a decent choice for introducing children to DnD. It is also more restrictive in its settings than its first iterations. Examples like Explorers Guide to Wildemount and the Uncaged Modules on the DMs Guild.
Pro Advantage rule
Rolls 2d20 chooses best. This dramatically makes all classes feel the same and moves away from distinct, interesting classes.
Pro The next best DnD for young children
After 1st edition/basic it is the most simple entry into DnD for a child of 8-11 years old. Important to transition children out of 5e around 11-12 years as it seriously stunts creativity and the overall roleplaying experience achievable with other systems.
Pro Slightly encourages character immersion
A few core aspects of 5th Edition exist solely to encourage thinking in-character, including mechanical rewards for good roleplay and detailed character backgrounds with lasting effects in the game. Of course these mechanics are shared for all versions of DnD.
Pro A good mix of the best rules of the previous D&D editions without the worst things
Cons
Con Immersive play, not free form narrative
Unlike some modern rpgs, D&D is designed to place players into an immersive, character-focused role within the story: the Dungeon Master is in control of the enviroment, non-player characters and many aspects of meta-plot, and must work with the players to create a coherent character with a background that fits the play world (no making it all up as you go along). Players who dislike not having equal narrative control to the DM may find this hard.
Con A bland mix of previous D&D editions with some of the worst thinkable new rule additions
Con Needs a good DM/GM
D&D 5th edition or any edition is an amazing game but...you have to have someone that is a good DM/GM for the game to be fun. Starting out from scratch you need to have a DM/GM that is very well read on the rules and ways of doing things. For noobs of D&D the DM/GM needs to be able to explain and guide the new incoming players on the way the game works and how to progress.
Con Unrealistic and complex rules that often don't make sense
Most new gamers don't get the sense of the way D&D combats are handled (people seem to just stay there for hours hitting each other in the face until one goes down) and would feel bad when they propose a nice idea which has no way to be applied in the game through the rules and so the GM has to invent a way to show it's a nice idea without saying "no".
You have to wade through pages and pages of spells and rules to "build" an efficient character, and if you don't do it or are new to the game you are less useful for your party "by design". That's why it's "complex" ( if compared to a board game or a more streamlined RPG).
Rules often don't make sense compared to reality, for example a very agile character in armor would get no benefit from his athleticity "because you wear plate, you know" (plate armor weights as a marine backpack but the weight is perfectly distributed on the body, so it's even less encumbrance, some guys even did a video comparing them on the same obstacle-ride). AC doesn't make sense in general and the rules for healing HP are the worst: the more HP (high level) you have, the more time you require to get back from the same % of wounds: veteran heroes must rest more than greens.
Con Hard for new GMs
Compared to most tabletop RPGs, D&D gives the GM (called the DM here of course) some of the most power and responsibility. However the core rules and even the DM Guide mostly focus on detailed mechanics rather than “here’s how the game is played and this is how to make it fun”. Since there’s a big community it’s not hard to find articles or videos full of advice but nearly every alternative to D&D gives a lot more guidance in the rulebook for handling the human side of the game.
Con Almost no published material for 5e
WoTC has been super lazy since 3,5 and even that had only a third of the material available that TSR published for AD&D 2e.
Is is sad that WoTC after 7 years has not supported 5e or other versions better.
This is a great reason to look into 2e or 3,5e systems instead of 5e.
Con Almost no published material in 5e
WoTC has been super lazy since 3,5 and even that had only a third of the material available that TSR published for AD&D 2e.
Is is sad that WoTC after 7 years has not supported 5e or other versions of DnD better.
This is a another great reason to look into AD&D 2e or 3,5e systems instead of 5e.
Con Lack of granularity
Overuse of lazy balancing systems such as concentration spells and advantage mechanic.
Recommendations
Comments
Flagged Pros + Cons
Con Bland classes and races compred to other versions of DnD
Overuse of concentration mechanic, no racial stat modifiers and hardly any differences at all between races and classes, compared to previous editions.
Con Only popular because majority of players playing it are new and have not tried other systems
Only justification for the system is to let critical role bring more people into the hobby. Once players try Warhammer, Vampire or AD&D, they will have no need to return to 5e.
Pro New, popular & growing
This is the most recent edition of the game and is the only one for which official content is being produced. Do not expect to see new official adventures or splatbooks published for any of the older editions of D&D.
Pro Bounded accuracy
Bounded Accuracy is a core design ideal of 5th Edition. In short, it means the numbers don't get too big; this lets weak challenges remain relevant for longer, and strong ones become survivable sooner. In practice, it also places more focus on a character's inherent abilities and less on magical equipment than has been the case in recent editions.
Out of Date Pros + Cons
Con Not much material yet
As of January 2015, only the three core rulebooks and two adventure modules have been published.