Aside from the larger engine and HP, 4 cylinders vs 3, more weight, I believe they were identical tractors. No difference in physical size, height, wheelbase, etc. Also, the B3030 had a cab model available while the B2630 did not.
Kubota M8540HDC, L5740HSTC, BX2200, BX2660, John Deere 425&1025R, Case, Massey Ferguson, Ford
According to my dealer, when I was looking at B Series, the 2630 didn't sell well so he never kept them in stock and they were dropped when they introduced the B3000, gets kind of confusing.
Kubota B8200, then a Kubota L3130 HST, now a Kubota L3400 HST
Thanks to guys like von-mil and Tractordata.com you should be able to tease out some answers. Interestingly, my old L3130, with the lLA723 loader and 31 hp sure had a lot more loader size and lift than our newer L3400 with 34 hp and the LA463 loader. Hp isn't everything, except speed and PTO potential.