Don't be discouraged. Choosing a cartridge is a compromise. Accuracy (efficiency), barrel life and velocity.

You already know all the choices out there. Availability is a high priority these days. I 'settled' on a Shilen barrel I can have now instead of waiting for about a year to get a Bartlein barrel.

I also went with a 6BR instead of a commonly available .243 because of barrel life and it had the velocity I wanted. Same kind of reasons I picked a .308 and .223 prior to this. If I wanted really flat and fast then a 6mm Rem would have more capacity.

Given a particular bore size the barrel life will be how heavy and fast are you going to push bullets. Cartridge case design is secondary to those (but still a factor). Your .243 is a real barrel burner if loaded to max. If this is a hunter then barrel life really isn't that important But, if you plan on a lot of rounds down range, then it becomes more of an issue. Unless you went 'down' to a 7-08 or similar, there will be barrel life issues. Again, I would assume (dangerous word) that you would load it near max to get the performance offered by that cartridge. Flat and fast has it's price. :)

My advice would be to get what you want. If the PRC has the performance you want then get it. If you burn the barrel out down the road then get another one.

FWIW, if I wanted a flat and fast 7mm I'd probably go with the RM, RUM or STW. RM is the classic choice, proven even with military snipers. RUM is the biggest, but, may be too large for the bore and barrel length you will use. The STW is in between, maybe the largest practical choice for the 7mm.