I live in Seattle area where we get lots of rain and since the door is facing west we get enough sun during summer as well. Our exterior door door clear coat finish cracked up and started peeling off. I am in the middle of restaining and finish our exterior door and would like to know which of the two finishes would be best for our area, oil finish or clear coat after stain and what the preferred brand is.

the traditional material is spar varnish polyurethane, for its resistance to sunlight.

flexing and breathing of the wood will cause issues requiring frequent rework, however. I'm wondering if there is a better alternative in one of the catalyzed (two-part) professional automotive clear finishes. if there is a variant for bumpers and other flex plastics on a car, it might hold up better on living, breathing wood.

you'd have to check with an auto refinisher for that. it would have to be sprayed, and catalyzed auto finishes frequently are nasty stuff until they set hard, requiring supplied-air respirators and full body suits for the applicators.

If you want a long lasting finsh then use Bristal Finish. Any boating supply shoud have it.
Far more UV protection then any marine Spar I've ever used.
Drys fast and most often no sanding between coats. The more coats the longer it's going to last. Three should do it.
Always seal all the sides including top and bottom. If not the doors going to expand and contract more and just crack the finish.

Thank you Swschrad and Joe, sure appreciate the input. Joe do you know if the Bristal Finish would work with interior or exterior stain.
Thanks again for the input!

Any real high dollar boat yard uses Bristal Finish all the time, both inside and outside.