I have done the HUMM on an XR600 and a DRZ400. This was both road riding and off road.
I found the XR tall and heavy off road (I'm over 6 foot). You need to be pretty strong and competent on it off road. It didn't have a kick start and this is a real problem after falling more than twice -it really saps your will to live.
I used the DRZ this year and it made a world of difference. It is smaller and lighter and inspires confidence so you don't fall off anywhere near as much. And when you do, the electric start makes your life real easy.
The XR is reputed to be simple and bulletproof and the DRZ comes with a good pedigree too.
On the tarmac they are much the same I'd say, you are not going to do more than 50mph for long comfortably.
The XR looks better but the DRZ is better to ride unless you are a confident and strong off roader.