When I was new to online poker, and trying to decide where to deposit, I downloaded a few different poker rooms to get a feel for each of them. As silly as it sounds, FTP's fun, cartoonish graphics (and clean interface) was a big attraction point for me. I also stumbled upon the notion of "rakeback", something that I surmised was a good thing to have, and which apparently FTP offered and PS didn't, so that along with its (in my opinion) better looking software, swayed me towards building my first poker bankroll on FTP.
I'm more informed now, and take less frivolous factors into account in considering my preferred poker site
. I still play mainly on FTP because as a low stakes, low/medium-volume player, I get more out of their rewards program; their standard 27% rakeback plus Iron Man surpasses PS's VIP offerings on the first few levels. On the very highest levels of volume, however, no rewards program comes close to touching PS's Super Nova Elite. If I could attain that volume of play, I wouldn't think a second to move to PS.
I haven't dealt much with either site's support myself, but it's practically a cliché that PS's customer service is the best in the industry, while FTP's is the worst ever (unless you're a Black Card member, apparently).