Hey Bender, I took two SUP's and two shorties on last trip (well documented by the crew on here) and I think there are a few things to consider such as are you on a boat or land based? Also who are the other surfers you are going with?
Last trip we did was a boat trip to Telos with the whole crew dedicated to SUP so we were able to pick the best destinations that suited us.
I also had some great sessions on the shorties but 80% was SUP.
If its a boat trip you are on and you are going with hard core name break chasing barrell hunters, I wouldn't bother with the SUP as you will be surfing more crowded gnarly waves and you probably want short anyway. You will also definitely want a spare back up shorty as boards break very often!!!
Also be sure to take a decent step up!!
If the crew you are going with are more relaxed, then the skipper can seek out awesome waves less crowded and then you would love to have the SUP on hand.
Also if you are land based there can also be wave options less crowded where again the SUP is epic.
2 trips ago when I was just getting in to SUP i scored epic A frames all to myself for 3 hours! (with a borrowed SUP from the surf camp)

I am going again this year for a 3 week stay at Macaronis Camp with just a short board quiver, as I can't be bothered lugging 4 shorties, and then the SUP and paddles as well.
Sorry for the long reply but I hope it helps.....either way you will get the best waves you have ever had!!