SP1/Vibe
Fully electropneumatic, can be more efficient, simple maintenance, has the BlackHeart Board upgrade which gives the Vibe/SP1 eyes, tons of upgrades out there
If you do get the BH Board, you can either leave the QEV on it and lose the low force bolt feature and rely on the eyes, or take the QEV off and replace it with the stock banjo fitting and have both eyes and the low force bolt
YDNA found that a stock ion could max out at 23 bps anyways, so there's really no need for a QEV besides for efficiency freaks
