I would say 3.5 psionics made the best gishes in terms of
-Power gain
-Versatility
-Flexibility
-Ease of build
-Smoothness of build progress through levels
3.5 Vancian usually had to deal with
-Complex class level builds with often garbage prereqs resulting in jagged build progression
-Dealing with ASF in some cases
-Less flexibility in spell resources (prepping & slots)
2e multiclassing was ok, but spell durations and spell choices are not as vast or powerful as 3.5, at least from my limited experience.
5e works just fine
-The concentration systems puts the power gain well behind what one gains in 3.5.
-Affords you the kind of magic you need for the encounter at hand. Ever useful shield, energy resistance at hand for flameskulls, elementals, dragons, etc.
-Within the system the 1/3 casters work just fine, as the attractive gish spells are concentrated in the lower half of the class spell lists.
-In 5e, between concentration, limited spell slots and class spell lists, casters also do not steal the role of the tank or gish in later levels.
-A lot of useful gish spells are bonus actions or reactions, making the action economy and combat flow very straightforward. Less stress over acquiring quicken, or preparing extend/persist.
-Better flexibility in usage of spell slots than 3.5
