The first one is servicable, but it's the second one (3.5) that has the really neat stuff. Of course this might all come later in DDI with the ecology of this and that, but i would still want it in the core since they had the room.
Huh. Let's see what they do have:
4e:
Description of monster (including picture)
Evil and nasty
Hails from the Far Realm
Lives in the underdark, in places where it connects to the Far Realm
Some live in ruins, lakes, or old temples
Leaves slimy mucus trail
Bends creatures to its will, the most powerful transforming them
Served by kuo-toa
Telepathic
Tend to live alone, but sometimes brood together
Lairs populated with enslaved humanoids and slimy minions
Section for tactics
Speaks Dark Speech
3.5e:
Description of monster, including weight and method of locomotion
Secretes slime that smells of rancid grease
Kills all nonaquative creatures on sight
Cruel and intelligent
Knows ancient secrets
Has memories of parents and all they consume
Tactics with illusion
Enslave individuals
Description of reproduction
Young hatch from eggs and live with the parent for 15 years, serving them
Speaks undercommon and aquan
The coolest thing is the "ancient secrets" power that the 3.5 aboleth has. (Though the 3.5e statblock doesn't let the monster DO that!) Otherwise we have two slightly different monsters:
The 4e aboleth, an evil creature who has "slipped" into this world from the mysterious Far Realm and seems bent on enslaving humanoids to its will, served by kuo-toa; and the 3e aboleth, an evil water-dwelling creature who hates and kills anything that doesn't swim, steals the memories of all it kills, and uses illusion to draw the unsuspecting to their doom.
If I were to use the aboleth in 4e, I'd start off with some people acting strange and more recent kuo-toa attacks. Then the PCs would head to the ancient temple, now sunken, full of kuo-toa and their Aboleth Overseer.
If I were to use the aboleth in 3e, I'd have rumours of an aboleth in some dungeon, and rumours that it will tell you secrets if you pay the right price.
I don't think either one has the edge.