CZ 550 American versus Winchester Model 70 Featherweight
Having never handled either one, I offer you this wisdom.
There is something to be said for the same manual of arms. If you own a M70 already, and it gets the reviews it does, and you like what you've got, why switch? A bird in the hand is worth two in the bush right?
The M70 is something you already intimately familiar with and you like it. I see no logical reason for you to "chance it" on a CZ.
Buy the M70.