The Baikal 12/30-06 was a great gun, it was factory regulated for the rifle to shoot 100 yards and the shotgun to shoot 50 yards.  The Spartan 12/223 had a huge difference in windage between the 12 ga and 223 of 6.5 inches at 50 yards, which could never be fixed.  The Baikal/Spartan guns do not have a windage adjustment.  So the windage is either aligned or not.  In my opinion when these guns are work horses when you have one that is regulated correctly.  
The Valmet 412/412s have easy windage and elevation adjustments.  The finish and overall  manufacturing is much more refined.  Also, the Valmet has a Quick Detach scope mount that after having it if a very nice feature and multiple barrels can be easily fitted to the receiver.
As far as weight goes the Valmet seems to be lighter, but I never had a problem caring either or mounting either.
Great question...  I am interested to see what others think.