To be perfectly honest I don't know, there seem to mixed preferences about each different type.
The impression I got from reading forums was that up to 15mm it's okay to use extended bolts with a hub centric spacer but for anything 20mm and above it's recommended to use the variation that bolt to the hub then you bolt your wheel to the spacer with your original one's, so no need to worry about extended locking/normal bolts.
At the end of the day I'd think it's down to personal preference? Badger5 or Damien @ DPM could probably shed more expert light on it to be honest.
For me personally I'm opting for the bolt to hub so I can use my original wheel bolts, I'm running 20mm Delta Mics on the back and I've found a set of FK's (for the front) at a decent price too that i'll get eventually.
http://www.fk-shop.de/en/Wheel-Spac...tLoader&cnid=354d5d3cf1dd69924258555896a28242
Those FK's seem a good price. Might try 20mm/15mm set up...
I'm only on 40mm springs currently so hopefully no rubbing issues.