With the infrequency of having to refill 60 lbs of LPG, I would stay with the current bottle type you now have and look into a better step or platform to access them. The convenience/flexibility of swapping in a 20 lb bottle if you cannot find refill location while traveling should also factor into your decision.
We frequently use our onboard Onan and camp year round (use the heat), yet I cannot complain how often I have to change out tanks or refill them. When I tow my trailer, I even carry extra tanks filled so I do not have search for refills in unfamiliar areas. If I cross a station with good prices, I will fill up all my empties and top off the my partials.
