Thanks for your post. To me, it is about cost, compatibility, weight and features.
A factory donor rifle, especially a Tikka, Remington or Winchester 70 will be $500 - $700ish. I paid $700 for my Win 70. Sold off some parts on it. Normal truing seems to be $150 -$250….maybe not needed on the Tikka. Then are you replacing the trigger, bottom metal, etc? Can you sell the factory bits? Then, how well can you judge that the donor action doesn't need bolt handle timing, extractor modification, scope mount holes aligned. Also, you need a scope base and many customs come with one perfectly mated.
Compatibility is just that. Trigger tech will only recommend their top trigger for custom actions. Some don't have feed rails so they require center feed magazines. Some triggers cause cock on close or other issues for one action, but not all. Stock fit to standard inletting.
Weight….I really don't have anything to say other than action weight is really important for balance. The action is one of the few heavy parts behind the balance point. It is also key to hitting a weight goal.
Features….3 lug vs 2 lug…I like 2 lug for cocking force reduction. Tenon length, size, compatibility. Safety design…trigger or striker types. CRF vs push feed. I prefer CRF, but like an extractor that will snap over a rim. Interchangeable bolt face.
To me, the Bighorn Origin with CRF, is the best solution out there. Wish I understood better why I might want to use the other more expensive Bighorn actions??