Zerg - Very adaptive your end goal is to build up the economy to become an unstoppable swarm, and getting to that point is very easy tech wise as your production abilities are your bases, and you generally only need to build 1 building in order to be able to be able to produce (multiple) types of those units at once.

Actual execution of what Terran is capable can require really good unit control at higher levels, as you have to micro drops and map advancement well to keep your edges sharp when working for you. Terran - Very flexible you have so many things that you can do and switching tech is almost as easy as floating buildings onto different addons, so you can change your strategy and utilize drops to either get a commanding lead or claw your way back into a game after some big defeats. The balance of making it to the Death Ball requires a ton of teching and surviving until you acquire the tech without good utilization of casters, you will be at a bit of a disadvantage once your opponent begins getting their Tier 2/3 units until you can get your high Tier power units. Protoss - Very straight forward your units are supply for supply, stronger than the other race's 'equivalent' units, so a same supply sized army should be stronger than your opponent's. The first highlights the really stand-out good things, the second highlights some really stand-out drawbacks. Trying to remove any bias, here's how I'll sum up all 3 races in 2 sentences each.

Starcraft 2 new race