Stayed at Fairfield Inn 4 times, Regal Sun once (this August)
Fairfield Inn (rates paid £25-31/night), free wifi, free breakfast, fridge in room, shared facilities with other 2 hotels in the Marriott village, although had everything in FI without going to others. At busy times (Xmas, Easter etc) the traffic is a nightmare to get from here onto SR535 and into Disney, rest of year should be OK.
Regal Sun (rate paid £25/night) here there is a resort fee of $15/night unless you prepay in UK with a rate that includes it (ours did) the resort fee covers Wifi. We were upgraded to tower room with great views, I heard the motel style rooms we paid for are not as good. Great location, walk to DTD. We also had no hot water 1 day, no idea if this is regular.
For me it would be down to price, both are OK. If you are a breakfast eater FI has a nice basic selection, cereals, toast, etc. no good if you like a big breakfast,