G15's are older clubs, G25 is the current generation with G20's being the club in between. Ping still makes the G20's and I think they are a fantastic club. This doesn't mean the G15 isn't a great club as well.
That being said, a great deal is only that if you are getting what exactly what you need, and to be honest, that doesn't sound like it is the case. The fitter is recommending a stiff flex black dot and you are looking at a yellow dot R flex, which is wrong on two fronts.
If it were me, I would spend the extra money to get the G20's, and have the confidence that out of the gate you are getting exactly the club that is right for you. Also remember that the G15 used the AWT shaft and the G20 uses the CFT. I don't know much about the AWT, but I think the CFS is generally considered a much nicer shaft than the AWT.
I am not much better than your 22 handicap, and have to be honest, that getting fit hasn't radically improved my game. It has however given the confidence to KNOW that the equipment ISN'T the problem with my game any more. What I mean is that when I post a bad score, or miss a shot, it isn't because of the equipment.
If you get the G15's, you will have a future spend (to get them adjusted) and that means you will play this year with a club, get used to it, only to have to get used to it again next year when you get them adjusted to black dot. Additionally, you will always have that thought in the back of your head (are these clubs right for me).