I really don't know, I have never analysed the English team in depth.
I see them play in Match of the Day and of course the CL, and Carragher always looked a strong pillar in the Liverpool defense. But then again, he is central defender in Liverpool.
Manchester United has dissapointed me over the past 3 years, and Neville was someone who I thought as ordinary.
But I guess the difference is small, right back is not really a position were there are big quality differences. Maybe Neville is the better choice because he played with Beckham in Man U.