I have two sets. Vix and Snappy (from Rockler?). The real Vix have a much heavier spring in them.
I think the big difference is the drill bits themselves. The Vix have brad point bits with larger channels in the twist part and seem to self clean better than the Snappy which seem to have normal HSS bits. I do not know if the new ones are the same, mine are all at least ten years old.
They both will get clogged when used on pine and the other sappy woods, but on hardwoods, the Vix are noticeably better in my experience.
I clean mine during use by just drilling a 5/32 hole in a scrap of hardwood, and plunge the bit into that every couple holes. Sometimes running it backwards while doing this helps too. With pine, not so much. I think I will try spraying the bit as mentioned above also.
Rick Potter
DIY journeyman,
FWW wannabe.
AKA Village Idiot.