I don't have both but one of my close friends has AT&T U-Verse and I have Fios. In comparing the two, we found both had their perks but we both thought AT&T had the better deal for the money even though I really like Fios. With AT&T's TV offering, we found that their DVR can hold substantially more HD programming than Verizon's can. This is something big if you record a lot of HD shows or want to and since most channels are heading toward HD, unless Verizon updates their equipment, they could lose out to a lot of potential customers.
Another strike against Fios is the stutter issue me and a lot of others are experiencing. Basically what happens is you'll be watching an HD channel and for some inexplicable reason the show will just start stuttering (the video gets garbled and the sound does too) for a few seconds, straightens out, then does it again. The only fix right now, from what I've seen in reading forum posts, is to unplug power to the STB and then plug it back in. But, I have heard this gets corrected (this is speculation though) in the new firmware release 1.6.2. If that's accurate, that would be a major issue eliminated.
That said though, there are two things I really like about Fios. The first is the services practically never go down. In the time I've been on it, I've had it go out maybe once...in nearly 3 years. I find that to be very impressive so it's a major sticking point. It just means that it can be counted on when it's needed and to a lot of people, myself included, that means a lot. The second thing I really like about it is more with the internet than TV. I found that the internet services are very solid and while the TV service has gone down once in the time I've had Fios, the internet has never gone down.
Again, both have solid sticking points but in terms of bang for the buck, AT&T U-Verse is offering just a bit more at the moment. I'm sure they will both be in deep competition for awhile though. If the world were perfect and I had my choice, at least for right now, I'd go with AT&T U-Verse for TV and Fios for internet if both were available in my area.
My father had Verizon FIOS in his home for about a year in Lewisville, TX. Then he got sick & moved to the an apartment near my home in Roanoke. Roanoke has AT&T instead of Verizon so he had to go with U-verse. He complained almost every day about the downgrade in Internet speed & TV channel choices until he passed away about 9 months later.
As far as the "stutter" on HDTV channels, I used to get that on local broadcasts HDTV through my outside antenna. Having seen FIOS in this area since it was first being test marketed in Keller, TX and compared it with AT&T U-verse for about 2 years, there is no way I will settle for U-verse. Until I can get fiber to the premesis, I refuse to change off of my DSL. BTW, my DSL is at 15.500 feet so it is only 768K/128K, but the 1.5M capped download rate of U-verse just doesn't impress me as being that much better.
I don't care that much about cable TV because I don't care much about sports.