I'd say they're more like what the majority seem to prefer, rather than unequivocal improvements. Colt had been lowering ejection ports and throating barrels for years, prior to the introduction of either the '91A1 or the enhanced models.
A lot of the "enhancements" were sort of half-hearted, with the magwell beveled only part-way around, a "ducktail" grip safety that some find less appealing than even the G.I. grip safety, an undercut trigger guard that some feel wasn't done very artfully. I prefer the "blank canvas" of the '91 to the enhanced models, as the latter have features that can't be undone if you don't like them.