I own an 09 TE310 and an 08 yamaha WR250R dual sport. The Yamaha loves the road but not so much the freeway (but it will easily cruise at 70+ mph), it loves to explore and is very easy to ride. It doesn't tire you out like a TE310 on long rides. The TE310 loves dirt, but not any road very much. Both are fuel injected. The TE is very tall and is not fun to mount or dismount, the Yamaha is noticeably lower and has an adjustable rear link that can trim off another inch or so of height. I'm 5'10" and I don't have a problem with the yamaha height...but the TE310 seat height can be killer if you get crossed up on the wrong side of a sloped trail.
I use my Yamaha for back country roads and exploring and occasionally some serious dirt riding (I did modify the stock blah suspension - the rear shock absolutely needs to be revalved). Lots of aftermarket stuff for the Yamaha, tanks, gear, etc., lots of guys use them for adventure even though the engine only puts out about 26 HP. It has a great tranny spread with 5th and 6th both being overdriven. Big alternator, strong subframe, good mileage. The Yamaha replaced an 08 KLR650 and an 04 DRZ400s dual sport - it is much more fun and nicer everywhere IMO. You don't even need to check the valves for over 20K miles and the bikes are bulletproof - lots out there with no real known problems. It doesn't excel at anything but handles everything well while being fun to ride.
The biggest drawback of the WR250R is it's weight. I weighed my TE310 at 275 lbs with fuel, and the yamaha is about 30 lbs heavier, although it's low cg hides the weight well. Since the weight is carried low, picking it up is nothing like a big bore heavyweight bike.
BTW, I'm an old guy too, well over 60, bad back and all.