port, what kind of casting do you do? touch and go or sustained anchor?
if you're new to casting a 2-hander, the skagit lines are the easiest to learn on. that's because timing is not as critical to pull off a good cast. all skagit casts employ a sustained anchor method, so you have time to stop, take a breath, and then set up and go. and it's made to cast dead chickens with heavy sink tips, and of course, a piece of cake to throw light summer flies, if you loop on a floating tip and a long leader.
the afs you mentioned is a longer, earlier version of the skagit line - sort of. it's got a longer front taper than a skagit line and therefore has a bit more finesse than a skagit.
but if you prefer the touch and go type of casts, then mid/long belly lines and scandi are the lines you'd want. and these are typically better for smaller to medium sized flies. timing is critical on such casts, because if you're too fast, you'll blow the anchor. too slow and the line sticks and kills your cast.
if you're fishing sandy and santiam, you'll most likely want to be able to swing weighted flies in the winter, so i would recommend a skagit line. getting the right weight (in grains) is vital to balance right with your rod. so is the length. for a 12 1/2' rod, airflo's skagit short is perfect. i've used rio's lines, but much prefer airflo as they're more durable and sweeter to cast.
hope i didn't throw too much out...