"Will I maintain MFSW controls."
Yes
"Info in MDI including answer/end call."
I don't remember at the moment, but I'm leaning towards no.
"Turn by turn directions in MDI."
No, you'll lose factory navigation. That page will simply disappear from the MDI.
"Does OEM RVC plug into this."
I think so. How do you have an "OEM RVC" though? AFAIK that wasn't available in the Mk6, or at least not in '12.
"Will the RVC parking lines be dynamic since I'm assuming I have a highline CECM."
Don't know, see above
"Dynaudio compatible."
I've read people say it's not, but it works OK with my Dynaudio. I think some VAGCOM coding could probably improve things, but I'd say I get pretty good sound quality.
Gain:
-Bigger, better screen
-Apple CarPlay, and also Android Auto on certain versions
-Can be turned on even when the ignition is off, and will stay on after you shut the car off (personally I like that, like when I park and I want to finish listening to something)
-Little nifty things here and there, like being able to display text messages in the "Phone" screen
-Interface is cleaner and more modern (I'm not a fan of that whole "circles" thing the RNS315 does)
Lose:
-Factory navigation
-CD audio
-SiriusXM
I've had my 330 for about half a year now, and for the most part it's working out ok...BUT, it took a couple of tweaks and tricks to get it that way, and it has so many bugs and quirks, it's kinda hard for me to recommend it. Keep in mind that most ones out there for sale are loaded with custom, third party firmware. That has introduced new capabilities and improved things over stock, but is also more buggy. You just have to look at the pros and cons and decide what your priorities are.