It depends; partially on how epic, partially on what you expect to encounter - If you expect to be hit by Dispel Magic a lot, then the higher default caster level of the epic items is handy.
If you are deeper into epic, and going for an AC monkey, then the extra point of AC is useful despite the cost after you have the non-epic Full Plate +5, Ring of Protection +5, Amulet of Natural Armor +5, +5 Tower Shield, et cetera, et cetera, as you can run out of other ways to increase your AC. If all AC upping item slots are filled, maxed out at the non-epic levels, assorted stacking spells are all already accounted for, et cetera, then about the only way to increase your AC any further is to go epic on one or more of the items. Ditto for the resistance items, stat bonus items, et cetera.
If you have to deal with Epic DR on a regular basis, you will likely want an Epic weapon, just to bypass it.
If you expect to get hit with a lot of Disjunctions, then you don't want epic items - at all; too expensive to replace - you want many safely stored copies of the maxed non-epic versions.
Really, it depends on what you are after, how deep epic you are, and your campaign environment.