Let me put it another way...
Five years ago you could find a nice M-28 for $400. These days they are more like $600.
I am not as familiar with the prices commanded by the -92s, but since they are still in production, I would bet they are not appreciating at any significant rate.
Edited to add: a quick search of completed GunBroker auctions (that is to say, guns that actually sold) shows numerous 92FSs starting at a sales price of $311. Quite a few between $350-400. One with 10 mags went for about $400.
If you had a two year old Nissan 350Z and someone offered you his near-mint '67 big-block Corvette in trade, would you take him up on it?
Two entirely different pieces of equipment, but one is worth far more than it's original sales price. The other, while a very nice functional piece, is still in production, and the price of used ones will continue to decline.
The major flaw in the analogy is that you woudn't want to drive the 67 Corvette for fear of diminishing it's value. (That and the fact that it's braking, suspension, a/c, and stereo systems are 40+ years out of date.)
But you can carry and shoot the M-28 all you want. If you ding it up, it will be worth a bit less than a mint one, but it will always be worth more than the -92.
And that is ignoring the difference between the 9mm round and the .357, which I hesitate to even mention...