[RarlyL8]

Track cars are apples vs potatoes, nothing to do with an M491 vs 930.
200chp increase over stock is easy with the 930.
Engine longevity has nothing to do with market value, if so a Camry would be worth more than a Ferrari.
The stock 930 is a tuned set of headers away from being equal to a Carrera in the drivability department. The 4spd gearing becomes perfect once you do that mod. The '87 Carrera I use for a test mule is modded to 200whp with an active exhaust and feels no different than the test mule 930 off boost. The only mod to the 930 (currently) is tuned headers. There is no off-boost bogging turbo lag with this 930, you should not need boost to drive around town. The Carrera on the other hand is in terminal turbo lag.
I guess it comes down to the '87-'89 M491 Carrera being the summit of Carrera-dom and the ultimate normally aspirated G-body, having the Turbo look. Got to question the Turbo wing on an M491 though, that's going a bit far. Love the look with no tail.