915 3 wood loft

Swing wise no but you'll gain more height, but loose a little distance

Both can get you to 16.5 so I would just go with whichever one you think would give you the adjustability you want. Normal 15 can be 16.50 - 14.25 where as the normal 16.5 gives you range of 18 - 15.75. I tend to hit all my clubs low so I use the 16.5 and adjust to 18 when playing soft, wet conditions.

I sould of explained better
I was thinking of getting the 16.5 version but as I can adjust my 15 to 16.5 my question was will my adjusted 3 wood perform the same way as a standard 16.5.
Is so then I won't need to change woods.

I should of explained better I was thinking of getting the 16.5 version but as I am able to adjust my 15 to 16.5 should it perform the same as 16.5 version at the same loft hence no need to change mine.

A 16.5 in the A1 sets up a little different than the 15 in the A4. As you increase the loft, the face goes from slightly open to closed. You would notice a little more draw with the 15 at 16.5. The 16.5 would be more open at A1.

Ok thanks
I thought it might have been more open at 16.5 but I prefer slightly closed

To clarify, the 16.5 and 15 at A1 are 0.5 degrees open. The 15 at 16.5 (A4) will be about 0.5 degrees closed. Prior to the 917/818 clubs I tended to add the 0.75/1 degree loft to woods just to minimize fade. Now I have the draw and neutral weights to adjust.

Both shafts are the same length. If you like close, then you need to loft down.