Baja Designs are just phenomenal lights. You can't go wrong with either.
10" S8 - produces 6350 lumens, comes in a variety of lenses and retails for about $400 with wiring. It also has a cool amber backlight feature which just looks so good at night.
10" Onx6 - produces 12,460 lumens, comes in a variet of beam patterns/lenses and retails for about $500 with wiring. No backlighting with the Onx6 series.
For an extra ~$100 you are gaining nearly double the lumens making the Onx6 the obvious choice between the two. We'd recommend either the driving combo lens (that's half spot half flood) which would provide a good mix of distance and width lighting or pure spot to reach far down those rural roads.
Black Friday deals on Baja Designs are here! Send us a PM, we'll get you hooked up. We've already got the marked down 10% off of retail, Baja is offering a $75 mail in rebate for either a 10" S8 or 10" Onx6 and we're including a free 20oz Yeti tumbler with all Baja Design purchases $300+.