Kempton by far is bigger, better, cheaper parts and more variety, more of the bigger companies go there, Whitewebs is very small, we went today and there was like 10 stalls and it was 4 pounds to get in!! Although I did get a complete exhaust for a B40 scrambler, clutch casing, cyclinder head and rockers and a swinging arm for 40 quid
But We also went to Kempton, much more, spoke to terry weedy company and got myself a complete rear wheel, with mint rim, and perfect brakes and galvanised spokes for 20 quid so I was lucky at both of them