Recs.
Updated
SpecsUpdate
Pros
Pro Start with all heroes
You don't need to unlock or purchase characters.
Pro Incredibly deep gameplay
For players who put the time into Dota 2 to get past the early beginner phase, Dota 2 can become an extremely satisfying game. There's a reason it's one of the most popular eSports titles in the world. The amount of strategy, skill, and variables involved make it a very deep game where anything could happen.
Pro A very diverse MOBA
This game has a steep learning curve, but it's well worth it. The games that came after Dota like League of Legends, Heroes of the Storm, Smite, and other lookalikes don't even compare to the complexity of Dota 2.
Every hero is unique and valuable in one team composition or another. The amount of versatility of each hero is amazing as well. The mechanics by far destroy any other Dota style game (MOBA) and that's what makes this game top tier in its genre. This game is the highest grossing eSport game in the world and will probably continue to be for a long time.
Pro It's very well-balanced
Gameplay is balanced in the sense that while other MOBAs would have only around 30-60 viable picks for the competitive scene, Dota 2 has heroes and strategies in the game that are more varied, which enables more heroes to be picked in the competitive scene.
Number of Heroes Picked in Dota 2's Recent Major Tournament in the past 4 months (as of July 2016) is 86/111 heroes picked and 100 out of 111 heroes picked.
To compare between Dota 2 and LoL pick diversity, LoL has 64 out of 131 champions picked for LCS.
There are also factors such as the ban/pick phase difference and the more rigid positions in LoL that may limit the viability for different playstyles and hero picks (typically it is 2 (AD, Support Bot) -1 (AP mid) -1 (Tank Off) - 1 (Jungler), with a possibility of double junglers in LoL).
On the other hand in Dota 2, there are a lot more different positions compared to Lol/Smite such as Duo Mid (1-2-2), Traditional (2-1-2), One Jungler (1-2-1-1, most similar to league), One Roamer (1-2-1-1 as well with the difference being the hero roams the map for kills to create space for the mid and safelane rather than farm the jungle which can weaken a lane), Duo Roamer (1-1-1-2, all lanes are weaker in lane presence with the tradeoff being they get solo experience with two aggressive supports roaming), Trilane (1-1-3, Aggressive or Passive Trilane) and Abandoned Offlane (0-1-3-1 where the offlane is completely left empty due to a strong duo or trilane on the opposing team).
More heroes are viable and balanced in Dota 2 partly due to the greater flexibility in laning. This can be attributed the mechanics such as creep pulling and creep stacking which allows the team doing trilane to make up for the shared experience between three heroes. Besides that, the existence of teleport scrolls that allow you to defend your towers or punish a tower dive also allows you to react and assist other lanes.
In pub games, any hero/lane/lineup can work, and it is more about your individual mechanical skills (understanding of hero, combo execution, map awareness, last hitting, timings, item builds, flow) over the lack of coordination and teamwork (on both teams).
Pro Very active professional scene
Dota 2 has one of the most active professional scenes in eSports today. If it's not the most active, it's certainly got the largest prize pools, coming in at over $20 million in 2016.
Pro Can be played online and offline
However, you will need to be logged in to Steam either way.
Cons
Con It's got a huge learning curve
Dota 2 has 111 heroes, all of which are unique from each other. It will take time and effort to learn which heroes you like to play, and become skilled with them.
Con Rude, toxic community
Many players feel free to flame and insult, especially in the lower ranks and from non-English speaking countries.
Con Matches are too long
The game is great but even just a single match can take a lot of time. And when you get to mid game and realize you already lost, you have no option but to keep dying and literally wait for the game to end.
Con Miserable community
Takes 100s of hours not to suck, and even then, you're still not going to be good.
Con You love and hate the game
While infuriating at times the addictiveness of the game keeps the players coming back.
Recommendations
Comments
Flagged Pros + Cons
Pro Deny creeps
You can kill your own low-health creeps to deny experience and gold to the other team.
Con Will consume a lot of time if you are not careful
Dota 2 has the potential to suck the player in.
Con League of Legends is better.
I add this just to keep parity with LoL page, attacked by dota fanboys.