Here's my $.02. Used cranks are like used condoms, they're fucked and someone elses mess. When they shit a roller from the rod big end and it makes it's way to the top of the piston, it's not pretty. Ask me how I know this, LOL.
You've got to set a budget for your engine, otherwise you'll either run out of money, or won't have the supporting pieces to do it right.
One thing that hasen't been mentioned is that depending on the porting, sometimes a stock stroke can't be re-ported for a 4mil.
There're several ways to do a 4mil stroker. My son's is an unported stock cyl.long rod with head spacer and FMF signature pipes, makes good power, great tq, especially down low. If I had to choose between porting and a 4mil, I'd get the 4mil and port it later. With porting, you can always take more out, but you can never put it back.
BTW, no such thing as stroker pistons, you have stock (short) 110 rods and long 115 rods using the correct pistons for the rod length. Most strokers are long rod, tho you can get them in short rod if wanted (not common).
Be sure you are building an engine that will suit your riding style AND area. I presume the trails in Vt. are kinda tight, technical, rocky, muddy. You'll be eating clutches with a light-switch powerband that it seems some are suggesting, JMHO.
While Vito's SS piston are good, don't know if they are offered for long rod crank.