It all depends on what you want, IMO. Both are great guns. I have the 4" 627 Pro and it's a really fun gun to shoot. And having 8 rounds in the cylinder is neat too. But a 44 Mag is in another league, power-wise, from the 357 Mag. And another thing to consider too is ammo costs. Do you reload? If not, it will be more expensive buying factory 44 Mag ammo as compared to 357 Mag. So your per round costs will be higher for the 44 Mag, but not double the cost or anything like that. And the 44 Mag has a higher amount of recoil than 357 Mag too.
Of course it is up to you to decide. I'm just throwing a few thoughts out for you to ponder and maybe help you make your decision.
I'm sure that either way you go you will get a revolver that will give you a lifetime of fun at the range or hunting.