I could be wrong because its a confusing subject but....I think the side vu transducers only come as 600w so if you want to use sidevu AND the 1kw down sonar capability you will need 2 transducers. The 8612 does have multiple inputs....but if you have two (with sonar) then thats a moot point...
7412 can come preloaded with G2 charts vs 8612 with G3 charts...dunno if that is that important.
Love to spend other peoples money so I say 86 but if were me I'd be maximizing my dollar and staring at every possible combination for months....
you'll need autopilot too and the heading sensor will allow your radar to use MARPA