The bike company doesn't really matter for your first bike (Kawasaki, Suzuki, Yamaha, Honda, KTM).
They're all great, they all have differences, but even if you decide to ride another bike in the future, it will only take 15-30 mins to get used to it.
But for your first bike? Definitely no 250.. unless you get a thumper (4-stroke), but still, that's a little intense. I started off around your size on a CRF150F, but i easily out grew that trail bike. I recommend a CRF150R Expert, thats the motocross version of the bike I had, it's a lot faster due to the engine modifications, etc. or an 85 2-stroke..