Lanefan
Victoria Rules
Depends on the Wizard type; a charmy-type will also want Charisma as high as possible; and at least 13 in any case if you ever want Leadership. (then again, the main wizard-type I played in 3e had rather poor stats across the board other than 15 Int, I think her Con might have eventually made it up to 12* but I was putting her boosts into Int and Cha as I wanted Leadership)While that sounds intuitive, it practice fighter's in 3e tended to have lower CONs than wizards.
The reason is that a fighter typically wants a combination of Strength, Constitution, and Dexterity, while a Wizard can safely dump stat everything but Intelligence and Constitution.
* - very late in her career she got hold of a +4 Con-boost item which got it to 16...and then she died.
That wasn't something I saw. Fighters in our crew sometimes went Con first, Strength second, and who needs brains anyway.In my experience the players of fighters typically don't want to completely neglect intelligence or wisdom, because they end up with no useful skills and poor Will saves. The result is that they tend to rely on less CON and rely more on their large d10 HD.

Depending what you're trying to do, yes. Then again, my wizard would have given her two front teeth to get two 18's!By contrast, the only attribute a Wizard player cares about aside from Intelligence and Constitution is Dexterity, even if it is of limited value depending on your build and play style. It's perfectly valid to play a wizard with 18 Int, 18 Con, and everything else 8's.
Might be one of the reasons but it's certainly not the only one; 3e casters had a lot of other things going for them that 1e ones didn't, and this could be its own whole thread.In 3e, CON is every classes second most important ability score, and in practice wizards will tend to have higher CON than fighters. This is one of the reasons spellcasters are much more effective in 3e than they were in 1e.
Yep.1e AD&D is the only system where I've seen the large disparity in squishiness you suggest, and that's because one of the class abilities of fighters was they got bonus hit points from 17 or higher CON, where as the maximum bonus hit points for other classes capped at +2/HD (at 16 CON). Because players tended to roll first and then decide what to play, it wasn't unusual to have a party with a fighter of 17-19 CON, and a wizard with say 10 CON. In this case, you very much would see a disparity of 100 hp versus the 25 hit point of the squishy wizard, which is precisely the sort of thing that helped keep high level spellcasters in check in 1e AD&D. When that squishiness went away, as it did in 3e, it was part of the reason that balance between spellcasters and non-spellcasters was lost.
In the 1e-style game I play in we often cycle characters in and out, and in one adventure we had a 120+ h.p. fighter* running with a 25? h.p. illusionist. (I forget the illusionist's actual h.p. but it starts with a '2' - though you'd think I'd know it, as she's my character

* - who is now up to 137 h.p.; the all-time record in any of our games and it ain't even close.