The advantage of a .270 Win over a .22-250 for varmints is that it's way easier to spot misses at long range. If you miss with the .22-250 in a grass area, it's almost impossible for a spotter to see where the bullet went. If you miss with a .270 Win, 100 grain bullet, chances are it will kick up some dirt.
We started varmint hunting with .30-06s as practice for deer and it was perfect. If we didn't know the range, we'd shoot a bit low and often bounced bullets into woodchucks. We were very careful where we shot, so ricochets wouldn't be a problem, especially with the 150 grain bullets we were using at the time. A favorite handload, as I remember, used Sierra 125 grain spire points ahead of a moderate charge of IMR 4064.
I wish I'd had a .270 Win instead of the .30-06. I probably wouldn't have bought the .22-250.