Kono,
I have to say that I have never had a Sako but I have only heard good reports from the fella's that have. They seem to really shine as they come from the factory with pretty darn good accuracy. With that being said, I have to admit that I am a Remington fan (hardcore). I would have to shoot the two side by side to be convinced or converted I guess.
I owned a Sendero in .300 Mag at one time and why I traded it is beyond me. After the barrel break-in the rifle was a one-holer if I could hold it. I just shot it too much and developed a flinch and had to revert back to smaller calibers to get rid of it. I wish I still had it. I developed very accurate handloads with it in 150, 165, 168 and 180 gr Ballistic Tip and J4 (168) Comp. bullets and actually killed a few whitetails with it (one at a lazer ranged 435yds). The .300 Mag is right at home at that range and really just getting started. It is a good, accurate caliber and either rifle will probably do the caliber justice. Good luck, Johnny K.