I submitted the following response to this same question on the other forum, but you asked it here so thanks to the miracle of "cut & paste" you can enjoy my wisdom again... (Gag!)
It's very difficult to assign operating cost to aircraft such as these; there are so many variables that have a direct effect on the final costs. Factors such as annual flight hours have a large effect because there are certain indirect costs that you incur regardless of the time it is flown. Fuel cost is also a factor, but not a much of one as you might imagine. However, there are several fuel co-ops that most operators of this class of bizjet belong to get fuel volume discounts. They say that hindsight is 20/20 and that's really about the only way you can accurately arrive a true operating cost. Anything else is, at best, an educated guess. Granted, every manufacturer publishes figures, but there are so many caveats as to make them practically meaningless. Bottom line is this - if you have to ask, you can't afford one.
As for which one is better, that's a little like asking which is the better car - a Cadillac or a Lincoln? All of these airplanes will have competitive performance numbers. But it all really boils down to which one "floats your boat.” That fact that one or the other might have 300 NM more range or perhaps cruise .02M faster is, essentially, meaningless in the real world. If you needed an airplane in this category, you could safely choice any one of them and not get into very much trouble. (I’m also including the Global Express and Challenger 604 in this group.) “You pays your money and you takes your choice.”
Personally, my favorite would be the 900EX or the newly announced Falcon 7X (Essentially a competitor to the GV and Global Express.) Why? Just because I happen to like it the most. The Gulfstreams are real performers, but with all of that thrust they ought to be. The Falcons have virtually the same performance, but they achieve it with more “finesse”, if you will. Personally, for our operations I would much rather have the 3 engines. In my opinion, for extended over-water operations, three Garretts (or Honeywell, or Allied Signal or who ever they are this week) trump 2 Rolls Royces any day of the week.