Will this be a snowbike only bike? What's your budget? Do you think you're going to like to jump a lot?
If swapping back-and-forth in the summer, I would do springs only. It's a pretty simple swap on the yz and just replace fork seals at the same time and you should be good for the season. My bike is snobike specific, but i still just did springs because of my budget. .62 works really well by itself. I'm sure they could be made better with valving though.
If you are going to run the yeti kit then I would talk to Toby Till. Those kits seem a little more touchy in regard to the front end fork set up.
Oh ya, I ordered my springs from the dirt lab in Salt Lake City for about 170 bucks.