I believe the reason the lower powered intel was removed was due to being out of stock.
I can find out though.
there's not that much different between the processors. Among those 4 I would stick with either the MII12000 or the SP13000.
I've run the MII12000 for a little over 2 years now I believe. Keep in mind though that I use the CarPC as a very basic feature. Music, navigation, and occasionally movies. If you remove the glow on the buttons on streetdeck, you shouldn't have much lag at all with the MII12000.