I only have experience on the Senate. But I've heard great things about the Omni series from a bunch of people.
Jmac and Brooks got me set up on a radar vapor last year, and I'm sold on radars same shape between models platform.
Especially when youre just getting into the course (like myself) the difference between layup and core, is not going to make a massive difference how the ski feels and performs. BUT, the shape absolutely will. With radar, all skis share the sames shape as the top of the line vapor, but get incrementally wider to suit different conditions/speeds.
The Senate will rip turns like a vapor, but will give you more support for learning and when going slower. Get a Senate!