Pro Extremely intelligent AI
As the player levels up gear so will the AI, who are programmed to constantly keep the player on their toes. Being that the whole game is designed to allow the player tackle any level in a multitude of ways, seeing the AI always react differently makes for an original experience every time something is tackled.
Pro Large assortment of weapons and tools
MGS V has a lot of weapons, including pistols, shotguns, machine guns, and sniper rifles. There are both lethal and non-lethal variants, allowing you to find something suitable for any playstyle.
There are also many tools such as the Fulton device, which allows you to capture enemy soldiers and animals, sending them to your base. It's a ton of fun experimenting with new gadgets.
Pro Enemy AI adapts to your playstyle
The enemy will pick up on your habits and react accordingly. For example, if you use tranq darts to knock enemies out, they will try to wake up their comrades at first. Do this for a couple of missions and they'll immediately run to sound the alarm when they spot someone knocked out. This way the game expertly keeps you out of the comfort zone, having the later missions feel as tense as the first.
Pro Freedom in approaching a mission
Metal Gear Solid V gives players multiple choices on how to approach a mission.
You can choose to use stealth, taking out enemies only when it's absolutely necessary. You can run in guns blazing, killing everyone on sight. You can get on a high vantage point and take out everyone with a sniper rifle. Or you can call in air support to do all the work for you.
The choice is up to you and the game doesn't penalize you for sticking to a single way. This helps keep the gameplay fresh for a long time.
Con Micro transactions
Something often found in free to play games is microtransactions, sadly they are included in the multiplayer aspect of The Phantom Pain going so high as $79.99 for a bundle of in game currency that can be used for advantage in the online part of the game. Considering that MGS V already is a full priced title at $59.99, to see Konami milking their fans for never ending microtransactions is pretty disheartening, especially when considering they can be used to get a leg up over others in the multiplayer by easily creating more resources over other non paying players.