All of that neglects to take into account that the higher level a primary spellcaster is, the more options it has for making opponents' actions completely worthless.
This entire statement neglects what I said about being on the same optimization footing.
4 Pun Puns > 1 Pun Pun with +4 Levels - It doesn't matter that Pun Pun+ 4 levels has more options than 4 regular Pun Puns; whoever goes first basically wins.
Look at the Dragon Fire Adept build that can infinitely use its breath weapon and fly
at level 1. That's just potentially 1 of 4 of the non-Pun Pun party; your non-Pun Pun Wizard is going to 100% of the time neutralize all 4 of the opposition with 1 spell *and* go first? I don't think so.
Don't want to take it to ridiculous extremes? Don't want to take RAW to 11?
Then it's an even
simpler initiative battle; a battle which a party of 4 within 4 levels of the solo character will *practically always* win by having 4 rolls to 1 roll. But, 1 character with 1 level of Marshall(Bard/Etc/Etc) makes it that much easier. 4 boosted initiative rolls > 1 boosted initiative roll If even *1* of the party goes first, then the odds of the solo character +4 drops like a rock - but what about all the possibilities? All 4 go before? 3 go before? 2 go before? 0 go before? All 4 go before, AND don't KO the solo? etc. The solo character is looking at practically no shot of being in a good situation. This is all before we know ANYTHING about the details of the encounter; just that the party makes 4 initiative rolls to the solo character's 1 roll and there are far more favorable outcomes to the party than the solo.
At every optimization level for D&D 3.5 it's basically Rocket Tag. This is beyond well known. 4 guys have a much better chance of shooting the first rocket than one guy with 4 bonus levels - and it's entirely possible at practically every single level from 1-20 to arm a character with a rocket (aka a 1 hit KO or potential 1 hit KO) - let alone design an entire group of 4 rocketeers that are optimized to work together.
Since the OP basically was just airing a question, there are no parameters for builds. The boundaries of optimization are exactly what determines who wins this.
"Core Only" inherently limits non-Wizards. In Core, only spellcasters get their 1 roll, AoE, KO rockets from first level on. Most of the classes in Core don't have 1 shot KO's but *can* get rockets if you allow more books.
If you say "everything is open" then 4 Pun Puns > 1 Pun Pun +4 levels.
It's likely that the average game is somewhere in the middle which is going to directly make or break team 1 or team 2 simply based on what is or is not allowed.