Not sure I have a favorite caliber. I've shot stuff with a lot of different ones. I do have a rifle on order in .284 Winchester. It's a New Ultra Light Arms Model 20, coming in under 5 pounds. Should be a good fit for walking the hills of Idaho. Don't know when it will get here. Just put in the order and try to not think about it for months.
I am not a one gun hunts all or even a one gun hunts deer guy. I haven't taken as many deer as some have as we have a pretty short and restrictive season in Missouri when compared to neighboring states. I have however taken my share. With that said, every deer I have taken with a .270 win was a bang flop. Those with a .308 win has gone down quick, but some were not dead when they hit the ground and made a few ground kicks. The 6.5 cm has performed very similar to the .308. The other gun I have taken deer with was a .243 win. A lesser sample size with the .243, but of the 3 I have taken, no bang flops and no straight drop downs. They all took a varying amount of steps from about 6 to 50 yds. Admit I never had to track them .
257 weatherby mag has been my favorite the last few years. This year I grabbed several different guns to hunt with. It kept things interesting. I acquired a model 7ks in 7mm br late that I was able to use on 2 doe. I’m thinking I’ll be grabbing that gun a lot!