If you drive a Ventana with it's Comfort Drive, you will be very impressed. It a pleasure to drive even on long trips.
The tag axle adds two more tires to replacement costs and does reduce storage. On the other hand it makes for increased stability, especially if it's windy or a semi passes you. It will give you more carrying capacity, and additional wheels for braking, when you have to make a fast stop.
If you are not going to do much boondocking I would opt for the all electric. No propane issues nor tunnel restrictions.
Without knowing your budget new vs used is difficult to say. If you opt for a used (and that's a good idea), look for 2-3 yrs. By that time all the little issues will have been fixed and the biggest part of the depreciation will have occurred.
Good luck with your search. Let us know what you decide on.