i play x3 mainly because of 2 reasons:
1) in full xmax, most of the time mobs feel more of a grind than a challenge.. there is no fun fighting tons of satyrs.. this changes in later parts of the game but i don't really like spending too much time fighting ordinary mobs
2) i want to fight 3 bosses but i don't want to get overleveled.. i tried x2, x3 and full.. x3 feels just right for me.. i usually finish act 5 legendary at around lvl 77
and yeah after playing xmax then going back to vanilla, lots of places feel empty.. i feel it even in x3.. the only time i go back to vanilla is when i complete quests that are bugged in xmax