which action for a 6.5 creedmoor build? bighorn tl3 or curtis axiom/vector

TL-3 if you are considering any sort of 6BR based case like the Dasher. More trouble free feeding from magazines.

I know you're already aware of feature differences, but the quick disconnect firing pin spring combined with a mechanical ejector on the TL-3 makes for a very handy reloading tool. Literally takes one second to be able to do things like check the feel of brass chambering or do seating depth tests, etc. Wasn't a feature I considered much when making a purchase choice but I use it all the time and would miss it if I didn't have it.
 
TL-3 if you are considering any sort of 6BR based case like the Dasher. More trouble free feeding from magazines.

I know you're already aware of feature differences, but the quick disconnect firing pin spring combined with a mechanical ejector on the TL-3 makes for a very handy reloading tool. Literally takes one second to be able to do things like check the feel of brass chambering or do seating depth tests, etc. Wasn't a feature I considered much when making a purchase choice but I use it all the time and would miss it if I didn't have it.

This.

Fixed blade ejector and easily changed bolt face makes it all kinds of useful as well.