Actually, even if you switch and go with a mini as the second unit, you still gain IMHO. You gain some additional features, and you move to five total tuners instead of four, and you will never have any conflicts with a genie. There is never a need to worry with one unless you record tons of sports, where as you have to keep things much more organized as you mentioned to avoid conflicts now. Plus, you'd have the exact same interface and control of settings recordings on both tvs.
IMHO you gain. Now weather or not that's a lot of gain, that's debatable, but I think its mice personally to have the genie system. And just easier.