The Ford v10 in my 2005 PW Excel has a tow rating of 5,000 lbs which I believe is double the rating for the v8. Also the v10 has a 5spd trans with a tow haul mode and is a lot beefier than the 4spd trans in the v8 model. I recall people complaining about transmission troubles with their 4spd trans in the v8 equipped rvs. No doubt in my mind, I'd get the v10 which has a lot more power and gets approximately the same mpg.
Also think long and hard about the TS versus the TD model which has the twin beds whereas the TS has the folding one. People complain about the hard and lumpy beds in these PW models. The later models have memory foam in them which helps but is not always the answer. On my twin bed model I had custom innerspring mattresses made and I leave the PW cushions at home and the improvement is like night and day.