From a sport stand point, I couldn't really say.. it all depends on the preference of the person indulging in the activity.
I would assume he or she would say whichever one they found themselves better at or more comfortable with.
That being said, from a practical stand point I would have to say BMX. Simply because it offers more flexibility and stability when being used for their principle purpose which is for the use of transportation.
man i think bmx is way better than skateboarding. idk about in the UK but in the usa bmx is alot better, and more and more skaters around here are assholes and stuff. alot of the skaters here are posers [skaters by image].
i get the same thing here, if i am doing parkour and skaters come past they ALWAYS say ''do a backflip'' and stupid shit like that, but there are a few good skaters just not many
i love ridin my bike its my favorit thing 2 do iv ben ridin 4 like 7 years i also like skating its rad but u gotta have more balls to ride cus when u bail on a board u can kick it away from u on a bike ur fucked so yea bmx all the way bro