Is adenocarcinoma of the vulva more radioresistant than squamous cell carcinoma?  

In general, SCC responds better to radiotherapy than adenocarcinoma, therefore I agree with @Sushil Beriwal that I would advocate for surgery (if possible) for these entities - however, given their location (close to introitus), often they will warrant adjuvant radiotherapy. 

Don’t know about radioresistant as they are uncommon and anecdotally, have treated some with pCR. That being said, would favor surgery as part of the treatment of locally advanced adeno while could treat SCC with definitive chemo RT with surgery reserved for salvage.

No published data I am aware of on vulvar adenocarcinomas, but extrapolating from cervical cancer literature, I would consider them to be slightly more radioresistant. Agree with others that leaning towards surgery and adjuvant RT as indicated rather than definitive chemoRT if at all possible. That...

The vulvar lesions I worry about are SCCs in a patient with immunosuppression for whatever reason. They seem to be bad actors that recur locally and metastasize more than anything else.