Bike for 15 year old

Ok, I need some help. My 15 year old son has never ridden a motorcycle before and I need to get him something. I bought a Yamaha TTR 90E for him to get used to sport at a slow pace but now I have to step up to the plate since the TTR is way to small. So, I was looking at a KX100 or a KLX125, what would be the better bike for him? We will be doing trail riding so I am leaning towards the KLX125.

Thank you for your time.

Sincerely,

Jeff

Thanks for your replies.

I ended up getting him a KX100, it just seemed like a much better bike when compared to the KLX125.

Thanks again.

Sincerely,

Jeff