A heavier barrel doesnt make the rifle more accurate, it simply makes it easier to shoot the rifle well. In other words, the heavy barrel resists you moving it whilst attempting a shot. The inherent accuracy may well be better with the Tikka.

Since a 25-06 uses relatively slow powders, the long barrel length may well be an advantage. You may see some lose in speed, but I doubt you will see a major impact on your hunting ability due to a couple hundred fps loss.