WB2 is an astronomical improvement over the first game and stands as one of the best entries in the entire EDF franchise. It's a hard pick between this and EDF 6, both games refine and fine tune the EDF formula in different ways and both stand high above all the games that came before.
Like the first game, this is a more arcade style take on the EDF formula where you control squads of soldiers in much faster paced missions compared to the main series, with a focus on collection new characters and building a team. The formula sees a lot of refinement in this game though, especially where those collectable characters are concerned. All of the characters have more abilities now than they did in the previous game (and all the new characters have enough abilities of their own to match) and there's a wider number of weapons. Generally all of the characters are also a lot stronger, nobody here really feels outright useless like some could feel in the first game. The 3 variations of each character have also seen a change, to match the change made to the game's accessory system. Now every character can equip 2 accessories, but they're split into multiple categories now and each character's accessory slots will be specific to a certain category of accessory. Rather than having slightly different stats, the 3 variations of each character now all are identical at a baseline but the accessories they will be able to equip are different. This keeps them distinct enough to have reason to switch between them without also creating blatantly correct versions of each character like WB1 did.
The difficulty (initially) is a bit lower than a standard EDF game, though this game does get more difficult compared to WB1. The mission count has massively increased and along with it so has the variety and scale of those missions. Many levels here are far larger scale than anything seen in WB1, and the roster of enemies is incredible. WB2 may just have the largest variety of enemies across any EDF game, taking the biggest hits from every single EDF game as well as adding a handful of completely original new enemies that fit in perfectly with the pre-existing roster. The game mixes and matches these well to create a lot of dynamic and interesting missions and the game never stops introducing new things throughout it's entire runtime.
Every strength of the first World Brothers game is still here and improved upon, while almost every flaw has been ironed out. World Brothers 2 is an incredibly fun horde shooter, and what it lacks in some areas compared to the mainline EDF series it more than makes up for in it's gameplay variety and mission design. If you have even the slightest interest in the EDF series there is no reason not to play this game.