The CZ550 weighs over a pound more than the Winchester. It would be good for you to handle a CZ & compare how it fits you compared to the Winchester.
CZ550's are reliable & accurate rifles, but so to is the Winchester model70. I haven't actually handled the new Winchester Model 70, but only hear good reports. Even though I own a CZ550 in 375H&H , if I was looking for a 243, I would probably go the Winchester.