I would have no reservation using a 270 short mag. Both of those load choices should work well...
Try for a quartering away shot behind the shoulder as the lungs are somewhat hidden, but with a partition you should be able to pound right thru if you had to.
I have had real good luck with a 270 win. so you should be good to go.
One was taken at our camp in AK with a 270 wsm. First shot was good. He put a second in him for good measure. The grizzly did not go more than a few yards downhill.