Ok here's my take..I am new to bikes but have crammed as much info into my head as possible in the past year or so..
the XR650, while having TONS of power..is a PIG..VERY HEAVY
if you are going to be doing any dirt riding at all, you will regret it....I like it as a 85%street, 15% (or less) dirt.....not fun when you drop it and have to pick it up
DRZ400....GREAT BIKE!!! I loved mine......the way I always thought of it was it was designed for 70% street, 30% dirt....
I rode my DRZ about the past 6 months, put 2k on it mostly dirt riding.....it as well, was too heavy. THe DRZ got about 60-70mpg's.....One day out learning to hillclimb I swear I dropped and picked up the 315# bike at LEAST 20-25 times
KTM
most, if not all KTM bikes can be made street legal. You find this out by looking at the title. Dirtbikes and quads will have "off road" or "OHV" titles....
KTM's come with actual motorcycle titles....most just needs a light switch, brake light and couple of othejr things to make them street legal
I view the KTMs as 90% dirt, 10% street
I just bought a KTM 450 4 stroke....oh man, I friggen LOVE it....tons and tons of power, but very linear and not scary..this bike gets about 35-40 mpg's...maybe more, but the thing sounds so good I cant help but crack the throttle muchy more often
If you are looking for good power, docile but fun....road>dirt--go for the DRZ, you will not regret it...they can be had for 3-4k with very low mileage and maybe 1-2 yrs old...I bought my DRZ out of convenience...I got a SMOKING deal and it was only 5 minutes from my house....I used it for 6 months as a learner bike and sold it for a profit
make yoiur decision based on where it will mostly get used....if youre going to keep to the dirt mostly, then ride to work every so often..KTM baby!
if youre going to street it the majority of the time, and occasionally hit a dirt road..the DRZ is the perfect out of the box true dual sport bike
Weights:
KTM 450 with FULL tank of gas: 280
KTM 300 2 stroker with about 1G of gas: 242
DRZ is about 295 dry, add 20lbs or so for gas, oil,fluids
At 280 the 450 feels like it weighs 50-60lbs less than the DRZ..I assume this is due to the weight distribution with the DRZX being more top heavy than the KTM