After purchasing two Shilen barrels in the past year and enjoying all that they offer, I probably won't be inclined to buy many more factory rifles. The exception to that would be if I wanted an accurate, low cost hunting rifle which wouldn't see a lot of rounds. Putting on a new barrel gives you the ability to specify the exact barrel length, twist, and contour that you want. It all boils down to what you want out of your new rifle and what you plan to do with it. With all of the quality factory rifles out there, neither of your two options is a bad one.

Since you want a 6mm cartridge, I will share with you that I recently assembled a 6BR Norma rifle with a Shilen bull barrel and am really enjoying it. It's stupid accurate with minimal load development and an easy shooter.