It is more expensive but yes, your fitter is correct.  I'm wondering if he had the shaft available to test?  On paper, the spin rate may decrease ever so slightly, but it is a much different shaft.  Since the numbers may be slightly different, the factors I would be studying are your ball flight downrange and your sense of control and confidence. 

Thanks Ryan-

Actually I played 5 rounds of golf in Phoenix with the Fujikura Motore Speeder 7.1 Stiff and as usual I was very impressed.  I took into consideration the ideal conditions I played in Airizona.  later in the rounds I started snap hooking my drives, never leaving out to the right even when adjusting the head on the 910 D3.  Overall it was a 8 out of 10 but I think I can get even better results. 

Ball flight was mid and strong although we did have some winds we dealt with when playing Legacy and Troon North. 

My longest drive (longest ever in my 4 years playing) was 364 yds in the fairway so needless to say it was great. 

My concern is that I am from Illinois and know that we never have ideal conditions.  I think I might be better suited to a slightly lower launch-lower spin shaft like the 7.2 or a House Of Forged Great White Shaft.  Something heavier where I never lose sight of where the club head is.