I think you need to realize what was given to you at the fitting, vs. you're current set... which is apples to oranges. Then your decision will be more about if you want to change to game improvement irons or not... vs. about switching to regular shafts.

A) Swing speed - The shafts in the fitting are lighter shafts, that will automatically increase your SS... because they're lighter.
B) Distance - The irons you demo'ed were game improvement irons. Look at the lofts compared to your current set... That would be your correlation to distance.

Your fitting wasn't apples to apples... if that were the case, then you may have a case to just change shaft flex. You came in w/ player's irons made for more control, and you tested game improvements made for more distance.

Sounds like it's time to get re fit by a Titleist fitter if you plan to stay with Titleist. There are so many shaft options available. Don't try to figure it out on your own..

I think that you will find that the M1 7 iron is more like a 6 iron in loft. It is really hard to compare irons across manufacturers as they all use different values for their "standard" lofts.

Go try a fitting with 716 AP2s, I bet you can pick up a few yards!

I played TM SLDR irons until I switched to 714CB's a couple of years ago.
Can't compare one to the other as the lofts on the TM's are alot stronger than the CB's, which is probably about a club difference in the same iron in both brands. Titleist can strengthen the lofts by up to 2 degrees to minimize the differences., but that also affects the bounce 2 degrees If you pick the ball more than you dig ( so to speak), you should not notice a difference in the bounce.