As long as you can pay extra or lump sums without penalty no, much cheaper than a personal loan. Even with costs it can still work out better.
I know that, we pay a meagre £100 a month extra on the mortage because it all makes a difference. But if he isn't doing that, which most people never do, it would cost a fair chunk more if its spread over 20 years at 3% instead of 5 years at 6%.