I think that it would be a close match, but in the end it would be Riley who would be left standing. True, Gunn has more experience fighting vampires, (demons are another story. If you recall, he and his crew never fought demons until after meeting Angel) he had little or no experience fighting anyone with the kind of specialized military training that Riley would have no doubt have been expert in, both with weapons and hand to hand. This isn't the old story of the trained martial artist vs the experienced street fighter, it's the case of the experienced street fighter vs the man who has almost certainly had formal martial arts training PLUS been schooled in just about every dirty trick and unconventional form of "take him out before he takes you out" fighting available anywhere in the world, from Mauy Thai, Kro Magda, and Russian Sambo to street fighting and the use of any conceivable, as well as quite a few INconceivable weapon available or improvised. Gunn would have determination, strength on his side, but Riley would have those plus formal training on his side, and that only includes hand to hand. Riley's weapons skills would blow (literally) Gunn out of his socks before the fight ever really got started.
