My only argument was that the Wizard is superior to the Psion because he can create a costless copy of him as a standard action. That is, after casting Time Stop as an immediate action (Celerity). I'm not sure that this argument has ever been countered, but if it has I apologize for the spam.
It has been countered by pointing out the Erudite, which is a variant Psion and therefore counts. The Spell-to-Power variant Erudite can learn spells as powers, which means psions (of a sort) can learn Ice Assassin, Time Stop and Celerity just fine.
I'd further add that if one wishes to use the spells as standard psions, one can learn the power in various ways from an erudite (for example, using Psychic Chirurgery). Therefore particular spells available to wizards cannot be used to argue that wizards are more broken than psions, because any spell the wizard can cast the psion can learn too, if necessary.
Oh but from the beginning I was assuming that the Psion already knows every single spell in the game.
I am waiting for someone to explain to me how the Psion can manifest a costless Ice Assassin as a standard action. Then, once this has been established, I'd be curious to know how a non-Epic Psion could actually manage to learn Ice Assassin (or any 9th-level spell) in the first place, but that's secondary.
Anyone can manifest a costless Ice Assassin as standard action once they reach level 5:
Step 1) Buy Candle of Invocation.
Step 2) Call Efferti/Noble Djinn.
Step 3) Wish for Belt of Magnificence +999999999.
Step 4) Wish for Staff of Wish with Googleplex XP invested in each wish.
Step 5) Wish for Staff of Time Stop (Or Maximized Time Stop).
Step 6) Put on Belt.
Step 7) Use Staff of Time Stop.
Step 8) Wish for Rod of Maximize (Can you use these with staves? I don't know, it doesn't really matter, it still takes you effectively zero time to anyone else to do anything).
Step 9) Depending on what you rolled on your 1d4, spend rounds Wishing for staves of Wish with each charge of your Wish staff.
Step 10) Spend your last Time stop Round Readying an action to TimeStop (Maximized is possible).
Step 11) Once in Time Stop again, spend all your rounds continuing to wish for more staves of wish.
Repeat 10-11 about 30000000 times until you have more staves of wish than anyone could ever care about. Occasionally stop to Wish up more staves of Time Stop before the current one runs out.
Step Whatever) Start using staves of wish to wish up staves of whatever other spell you want, such as more Time Stops, and Ice Assassin staves, and whatever else.
Step Ice Assassin) Use Staves of Ice Assassin to make a whole bunch of Ice Assassins under your command.
Step What Even) Now the Time Stop chain has to stop, so that you can order all your Ice Assassins to do whatever you want them to do, and then give them all staves of Wish.
Step Hey What About This) You should probably wish up a staff or right of MindRape, and use that to make all the Ice Assassins not want to kill you, so you don't have to worry about them distorting your orders or whatever to kill you.
EDIT: Actually, that probably doesn't allow you to Ice Assassin, since casting time is 8 hours and I think items carry over the casting time (although I'm sure there is some way around that) so I guess you have to wish yourself to a timeless plane to cast all your Ice Assassins (and then Mindrape them, and then give them all staves of Wish).
Or you could just wish up a Psionic item of Schism, if that allows you to do it a Psion it would all you to do it as a Commoner with items.