Dave I have towed with both .
with a 30 foot trailer the less over hang on the back the better but they are not bad if you use the stabilizer bars the mileage will not be a lot of difference with either engine really .
But let me give you a little bit of a advantage right now I do a lot of buying and selling for a large car dealer and a auto auction and don't just go to a dealer and buy a motor home and let them tell you how good of a deal they are giving you there is a lot of motor homes at the auctions now from repos and dealers trying to get rid of them and they are cheap now.
for perfect example last Thursday they was a 99 winnebago road master 32 foot with 24k miles on it with a 454 sold for 8500.00 dollars and a 98 ford cruise liner with 27K on it with a V-10 and it sold for 11.200.00 they are really cheap right now that market is really struggling now and around here we have a lot of motor home dealers that would love to sell one .
hope this helps and good hunting. Ron