I was in your situation a few years ago.
I started on a KLR650. Great bike, bad choice for me due to where I ended up putting it with a limited skill set
I started riding a 250 about a year ago and my riding vastly has improved. Light bikes are so much fun and allow you to make mistakes that would be painful on a large bike. In January, I managed to total my KLR and upgraded to a 690 enduro for dual sporting. It's more bike than I can reasonably handle in terms of power, but it does things I would have had a really hard time on the KLR. It's a handful on single track due to the steering geometry, but is a better all around bike for what I do compared to the KLR. If I am going out for a single track session, I take the 250 for enjoyment. If I am on a trip and happen to do some single track on the 690, it's managable.
So, if I had a time machine, I would probably have originally selected a Honda 250CRF-L over the KLR650 for an introductory dual sport. Easy maint, lower costs, lighter weight. Not the greatest for long highway trips, but manageable for leaving home and getting to trails. Had that been my original choice, I would likely still be riding it. A DR650 is a nice dual sport option and I ride with a lot of folks who enjoy them. Inexpensive to set up for adventure riding. For your application though, it might be a bit heavy and less fun on technical trails.
I highly recommend buying used. There are plenty of people who buy 250s and either fall away from riding or change their riding focus, which equals nice savings for you. If it turns out to be the wrong bike for you, it is less painful to sell and switch to a new ride. Buying new, you might end up staying with the wrong bike for too long due to the depreciation.
Hope it helps,