A friend of mine has the 5" 629 Classic and I have the 6.5" version. As mine is strictly a range gun and never carried I actually like having a little extra weight when firing 44 Mag loads. The only 44 mag that I owned that was more "pleasant" to shoot than the 6.5" 629 was a 10.5" Super Blackhawk.
Either barrel length is a great choice , the gun shop only had a 6.5" 629 the day I bought mine , if they only had the 5" model available that day I would probably have a 5" today.