Well i think the higher the tier the item is (rare,epic,divine) the more stats it gives. Im not talkin about attributes but more "slots" for stats. For example a blue ring provide +1 to pyro and +1 to geo but an epic provide in aditional to those +1 to something else and a divine +1 to something else. Also it effects the damage on weapons by a little. The only problem i find is that after a while you will be forced tro change gear every 2 lvls at max due to stats inflation.
