http://www.tomshardware.co.uk/radeon-r9-270-benchmark-review,review-32918.html both reviewed here
so gigabyte runs cooler, bit louder and slightly lower overclock, msi heats up slightly more, quieter and has a better (20mhz not that you'd notice it) overclock.
i don't own either but i suspect if you play with the max temps/fan speeds you match msi 's values or better, the windforce cooler is great. they traded noise (which is still acceptable) for the lower temps on the default settings. msi allows theirs to get hotter so as not to spin the fans so fast.
edit: get the better price or longer warranty, they are both great cards.