Brian,
A 1-9 will work very well in the 6-284 with 105 gr VLD bullets. 1-10 will be a bit slow I would say, even in a 30" pipe.
Conventional wisdom says a 1-8 twist is the correct one but I have found in the 6-284 with the Berger and A-Max bullets, the 1-9 works much better and allows a much higher top velocity potential without bullet failure or accuracy decrease.
With the 107 gr SMK, 1-8 or 1-9 will work fine as it has a thicker jacket. Also, I would stay away from the 3 groove barrels if you want to shoot the Berger or A-Max. Order a 6 groove as they are easier on these thin jacketed bullets and will allow you to drive them faster with better accuracy.
Kirby Allen(50)