Well, that depends.
A real Amiga will allways be more compatible than UAE; nothing's going to change that. Still, UAE is way faster than low- to mid-end Amigas, and It's easier to fit one computer into a room than fitting two computers in a room.
Unless you're really picky about image quality when emulating, or if you really have to be a "genuine" amigan, then I'd suggest that you stick to emulation. Besides, most Amiga HW is getting old; it'll be dead soon... :-(
