Whoever introduced the fixed headshell might have saved themselves some money but they didn't do anyone else any favours.
Another classic case of manufacturers selling folks short whilst telling them it was for their own good.
If you must upgrade then Option 1 seems better to me.
All turntables benefit from better isolation - some of them incredibly so.
Especially when as you say, "either TT will sit on a pretty solid wooden credenza".
If that doesn't satisfy you then you'll need to save up for something substantially better.
Decks such as the Technics SL1200GR or Rega 8 will also benefit from an improved isolation platform.
The best form of turntable isolation is probably another question altogether possibly involving the use of accerometers and stethoscopes.