Just on hour building generally, something to watch when choosing a rental is the rate that fuel is refunded at, some places put a ridiculously low cap on the price meaning you might be effectively paying an extra few dollars per hour if refueling elsewhere. Also, ask to read their contract and check the detail. For example, should you have a technical problem someplace then you don't want to be liable for the handling/parking charges that the local FBO may apply.
Has anyone done a league table of fuel refund rates, and other contract details? Seems to me that such things make a significant cost different once everything is totalled up. Just comparing the per-hour rental rates is a small part of the picture.
Accommodation value-for-money is another thing that bugs me, eg $35/night at some outfits will get you a discount rate at a very nice hotel, whilst at others all you're getting for the same cost is spartan student accomodation.