I'm beginning to believe that the root of this disagreement is that through a combination of houserules and favourable readings of the RAW ways and means has made wizards vastly more powerful than they normally are. Having done so, he worries that they are too powerful and looks for a way to balance other character types against them.
I don't have a "balance" issue in game...the wizard typically throws around three to four shift spells.
I simply recognize that, mechanically, there are more ways to raise spell power than to raise weapon damage.
Targeting skills are roughly equivalent. The wizard uses Discipline while a combat type will use one or more of Fists, Weapons, or Guns. The wizard may have a slight advantage in being able to use his single targeting skill at any range but it's probably balanced by the requirement for additional skills (Conviction and Lore). Depending on whether or not reactive blocks are allowed, the wizard may or may not need a defensive skill. Combat types do need either a defensive skill or a stunt allowing them to use their combat skill for defense. Overall, a wash.
Weapon / spell Power is a different matter. A combat type has two methods of increasing damage - use a weapon (which limits Fists' usefulness) or Strength powers (which don't help Guns). On the other hand, a wizard has three methods: increase a skill (Conviction), Specialties, and Focus Items. Specialties cost refresh and may be compared to spending refresh on Strength powers. However Conviction and Focus Items stand out, Conviction because it doesn't cost refresh and Focus Items because they're a relatively refresh cheap method.
To make matters worse, a Good (+3) Conviction pretty much matches the maximum civilian weapon rating. Since most wizards will increase Discipline and Conviction whenever possible, they're probably starting out higher than most weapon wielding combat artists. And, at the same time, he increases the number of spells he can cast.
Which brings us to a wizard's major weakness - the number of spells he can cast. But most combats don't last all that long and this can be ameliorated with enchanted items. In the end a wizard is capable of hitting harder than most combat types, he's got enough endurance to last most situations, and he's far more flexible.
When it comes to "game play balance" I really don't care. We're playing a cooperative game not a competitive one. It's simply a recognition of the mechanical possibilities.