I believe the major difference is the addition of fully adjustable X-pro trigger.
I just gor SFII in 300 win mag and it came with factory set of 3.5 lbs pull which is good for me. I believe you can adjust down to 2.0 lbs or up to 5.0 lbs. Also, I think the stock is a bit different on SFII then the old sendero. Old had a black stock and the new one is black with grey type. There may be some other minor differences.
The issue I have with mine, is that it does not always ejects properly and the case stays in the chamber, unless I rack the handle hard and back right after the shot. Do you ever have this issue with yours ?
Thanks