Cataraft girl - Why would you want a raft bigger than 12'?
If you're going to be rowing it without any passengers and go with people that have bigger boats you should'nt need a 14.
The bigger boats are heavier (i.e. harder to carry, store, etc), more prone to collecting more gear and people. You've already seen how the 12' handles some water, if your comfy in bigger water with it keep it and let the others carry passengers and the extra cases of beer
. I have a friend who routinely rows her 10' achilles bucket boat down lots of multi day runs. of course she carries no gear, but manages to convince someone (usually me) to carry her drybag. She gets to get surfed and acts as the safety boat and can go where no other big boats can.
Of course the alternative is a bigger fleet... and more toys.