i would go with a good 130gr. premium bullet for your 270win. sighted in at 200yds you will be 6.7" +/- at 300yds. the TBBC's would be a ideal bullet.or the sierra gameking's SPBT ( which i used this year on a buck at 50yds ) worked great.

as for a pick between the 7mmSTW or the 270win. go with whatever you feel comfortable shooting. but if it was me and if i had the $$$ good enough excuse to buy another toy