What will work better for my hair a GHD or the instyler..?

my hair is a couple inches past my shoulders, it is layered, and it's not thin but not think so kinda in the middle.. i have a chi but it's not the black one..it's zebra stripes...my hair will be straight but after an hour its all flipped around and i just end up pulling it up in a ponytail...help?!?!?!!?!?