The difference in meter speed will be one thing to centend with, but, IMO, the bigger thing to contend with with the i15's (coming from the Raptures) is the lessened forgiveness COMBINED with the faster meter.
I got the i15's and played them for a couple days then put them away. Until I can combine them with the GI2-SD2 balls that come with Legend status and slow down the meter without losing the distance, I'll stick with my TM Tour Preferred. The G10's are very, VERY good too and offer a slightly higher trajectory than the TM's.
I don't hit the ding very much as it is (I have good days and bad) and the extra forgiveness the TM's offer work very well for me.
To answer your question more directly...the i15's are ONLY worth it if you can hit the sweet spot with regularity. If you can do that, then yes.