The Bourns model feels smoother (almost too smooth in fact, so I feel it's not quite positive enough into the detents). The ebay type works fine, but is a bit heavy & grating. On balance, I prefer the 'feel' of the Bourns model.
Partly this might be due to the fact that the Bourns is 24 detent (versus 20 detent for the other). I'm after something around 18-24 detent with centre-push and I wondered whether I could find a compromise price/performance wise between Bourns and 'generic'.
Some of the eBay encoders have a thicker body, more like Bourns, maybe these would be better built?
I'd be interested in photos (& links to) of encoders which cost less than Bourns but which have been tried & tested.