Well, that's not much to go on. Frankly, it sounds a bit like bait. I suppose it's been a while since there was an SCT vs Newtonian slanging match, or a "my scope's better than yours" punch up.
You
had a 12" Dob and think it showed more details? Any side-by-side comparison? Or just going from memory? If not side-by-side, then there could have been vast differences in seeing and transparency. Did you keep detailed logs of conditions, time, target elevation, exactly what details you saw, etc.? Were you using the same eyepieces (doubtful, given large differences in scope focal length)? But, possibly, you may have a lemon. Quality of optics can be a factor, but without a controlled test, it's hard to draw firm conclusions.
When was the last time you collimated your SCT? It'll still need it, from time to time. The corrector may be slightly off centre - I (and others) have found that to be a potential issue - the cork shims can shrink/compress allowing corrector movement. Are you letting your scope cool down? A C14 will take a couple of hours, possibly longer.
No matter what scope you have, in poor seeing, planetary views are crappy.
An afterthought: Isn't your mount a G11? A C14 (and accessories) must be pretty close to the limit for that mount (not that it'll affect the planetary view - I'm just curious).