I'd say strength by a long shot. Id rather kill the monster faster than take less damage.

i agree this opinion ....and i play only arena ( dont like cata )

EE armors work great, especially in catas ( you can tank ) and they're still good in solo.

but in your case, a STR armor, if you're soloing AND with axes, will be way better !
It will add more damage to the constant damage of your axe and help you to kill monsters much faster

both^^but strengh>ee