The vast majority find that once they move to an SSD there is NO going back to a mechanical HDDs - Guess they Love it.
In terms of size: Optimum size is a 120/128 Gig SSD. In my systems (no games Installed) Windows + my programs take up about 30->35 Gigs. That would leave about 70 gigs free for games (Want to leave at least 10% of drive as "Free space".
80 gigs / size of game = Nr of games that can be installed.
Performance: Outside the Very fast boot time and program loads. If the game maps are on the SSD they will load faster, but game play (outside of loading new maps) you will see no difference.
Noise - SSD, no mechanical parts, No Noise. HDD, most are pretty quite when installed in a Case and fans running so may not hear. Note That the SSD will probably be lower power and less heat generated than a HDD. May therfore help in keeping inside of the case cooler which may allow fans to run slightly lower RPMs = less noice.
Reliability - Not good data (ie users using for 5 yrs), but SSD should be more reliable (ie upto the 5 yr point) again as No moving parts.
Choice - M4 a great choice (have two of them, one 128 gig M4 for OS + Programs and One 128 gig M4 as a work(data)/scratch disk. I have upgraded ALL my systems to an SSD - 2 desktops and two laptops.