I haven't stayed at the Fairfield Inn but I'm pretty sure they are mostly very nice.
Our room at the HoJo had numerous problems. The safe didn't work upon check-in, so we had to have someone come up to fix it while we were at the parks that night, sort of defeating the purpose.

The Internet didn't work until two lengthy calls to the help desk, and then a person had to come in to change out the boxes--they estimated 15 minutes but I think it was closer to 4 hours. We'd left the room by the time he came by, so I had to shout my computer password to my mom via cell phone since the engineer wanted to try the connection with my computer and I'd turned it off to conserve battery. The Internet is wired so you'd need to bring your own Ethernet cable (or request one of the few longer ones from them) to use it anywhere besides the nightstand. There were few electrical outlets in the room and they were almost all too loose to hold a plug--I had to use the bathroom's plug to charge my laptop, so I couldn't use the Internet and charge the battery at the same time. The air conditioning was fairly loud (and needed to run almost all night to keep up with the relatively mild June weather).
But, the air conditioner was plenty loud enough to mask hallway noises--the only morning I heard kids yelling at all was when the air conditioner had actually shut off. I don't think noise would be an issue there.
The walk was a little long--not bad at all if you don't have any health issues, but the humidity (?) gave my mom a lot of pain, and more than one night, she was not able to return to the parks after an afternoon break because the walk was too far. The beds were fine but I wasn't wowed...I'm not picky with beds, either, though, so maybe I wouldn't notice an awesome bed. No one else in my party commented about them.
So IF the rates were the same, my instinct would be the Fairfield Inn. They claim to offer wireless Internet (like most modern hotels) and are likely a nicer building, although I think they do have exterior corridors. I agree that the main reason the HoJo would be better (besides that the rates are probably lower in general) would be the pirate water play area, but I don't have children so that wasn't a big drawing point for me.
Good luck deciding! You'll have a great trip regardless.
