I’m wearing a set of the fakes just now as it happens. I got them for 20 something quid off ebay as an experiment – they took literally months to arrive.
I also have two proper sets so I can make a pretty fair comparison I reckon.
The fakes are made of noticeably lighter weight material – they will definitely not last as long as the regular ones. I actually use them for xc/commuting duties ‘cos they’re so much cooler than the genuine ones. The fakes don’t have the internal hip pads like the genuine ones either.
The fit is a bit different too – mine are 32’s but they are more like the length of a genuine 34. I actually quite like that as I’m a lanky git.
The clip/ratchet thingy at the waist isn’t as good as on the genuine ones – sometimes it randomly loosens off a notch.
I’ll be getting more genuine ones next time, if the 2 sets I have ever die that is…