I've owned both - I like the 3630 better because A: Built in Noise Gate and B: actually fits in the rack. (NanoCompressors are 1/3, but damned if I know how to mount them into a rack)
For the few extra bucks, the 3630 gives you the extra bit or two that make it worth it. - But I haven't used a behringer, so I can't provide input on that.