I don't want to get too far off the path here... because as it pertains to this project, you can literally choose what you want. I wont' force you to go with a Quad if you don't want to.
However, here's how I see it after having spent time with both:
CZ has plastic mags... Quads are metal.
Quads feed better, with less bullet deformation.
Quads have a "normal" safety like we're used to. CZ's is "backwards" and awkward.
Quad mag retention is awesome.
I believe the quad to have superior bedding interface.
Quads have a remarkably simple and very good sako/tikka trigger.
CZ has a high 90-degree bolt lift... and can limit optic choices. Quad's have 60 degree lift, with far better ergos when combined with DIP or KMW knob.
The bolt operation is much smoother on the Quad.
Not that it matters to those of us that are replacing the stock, but the factory stock on the quad varmint is superior to that of CZ's "varmint" offering.
...and we haven't even started on barrel changes, and the quad is superior there as well. This does not surprise me in the slightest, given a CZ can be had for
half the price. I believe that if CZ 455 was equal to a quad, equally configured... then the price would reflect it. It doesn't. I really wouldn't expect it to. If there is someone else that has owned both, perhaps you can weigh in?