Typically speaking, the Pro's are for tanks that have a height greater than 36".
For most pro's are not necessary, but like you said "It's just $100 more"....of course in your case is $1,000.00 when buying 10 of them.
I don't think it would be a good idea in general to mix and match the standard model with pro's simply because if you have them all running on the same program, then the Pro's will be putting out about 14% more than the G3's will because they have 20 more total watts of power. So unless there is a specific need for this, or they are running separate programs, I think I'd stick with one or the other for all 10.
What dimensions is your tank?
What corals are you planning to keep?