I've been (for the lack of better words) "drooling" over the Tikka Tac A1 chambered in 260 Rem. If I didn't have a human baby on the way I'd have one of those baby's on the way, maybe I'll name my boy Tikka and have the best of both world's,
The 260rem is a solid performer right between the 6.5x55 and 6.5 Creedmoor, with the poor marketing done the cartridge was overlooked when compared to the popularity of the 6.5 Creedmoor although I'm sure the ease and now well used social media pages also have a part in the self marketing aspect that gains the creedmoor a huge variety of factory produced ammo over the 260, and even old faithfull 6.5x55. All are basically identical in real world conditions, (Just saying no need to get into the 2" differences for hold overs with different loads from me) as there are lots of debates between them all puonded to death and realistically your holds will be very close to ring steel at distance. The Tikka Tac A1 in any of these cartridges would be a great combo I do like the layout of the platform and smoothness of my tikka. The 260 COAL is slightly longer but not as long as the x55 which is a long action, (and really I don't mind moving the bolt back and forth an extra milisecond for the x55) giving minor restrictions on Bullet seating depth in non-tikka actions, however in the Tikka action you can play with your seating depth just as much as you could with a Creedmoor with respect to the ease of changing out or the bolt stop, and running a long action Magazine if you found you really needed to seat that long skinny 150 gr out further to gain, I personally have never run into a seating depth issue with the 260 compared to the Creedmoor because luckily my rifles seem to have the sweet spot for different bullet seating depths just under mag length,
Long and short of it is If you are looking to Run Factory ammo, I'd suggest the Creedmoor for huge factory variety, if your handloading I'd suggest the 260 Rem, because it's got just a hair more gain, really though your holds will be very close with either cartridge in that platform.
My humble 2 cents! In the end of your research get the one YOU like most! The biggest aspect as you know is personal preference, Good luck!