You did not mention budget constraints.
Larger SSD's are a bit faster.
Buy a 500gb SSD, forget the HDD and be done with it.
But, otherwise, buy a 240gb ssd. It will be large enough to hold a bunch of games.
120gb is enough for the os and a handful of games. More than that, you will be needing to juggle game placement on two drives.
As to which, any Samsung will be good. Intel too if it is cheaper.
The PRO has a longer lifespan, but that is really a non issue for desktop users.