I've come across this same issue. I've ridden dirt bikes my entire life as well.
I've been looking into getting a 600 supersport such as the Honda Cbr600rr or the Yamaha R6.

After doing tons of research over the past few months, most experienced riders will say that even if you've been riding dirtbikes, it is a bit different on the streets. Everyone doesn't want to have a 300. However, I think it may be good to start on a 300, learn the ways of the road on a bike that can't go 300 mph, and to max it out on its capabilities. Then, move to a supersport. Not currently able to buy a bike this moment but that is what I have found.

Personally, I just want to get a supersport and be done with it. Learn on a bike with power and respect it. But, that's not what most I've talked to with experience will say. Good luck.

Allergies wrote I've come across this same issue. I've ridden dirt bikes my entire life as well.
I've been looking into getting a 600 supersport such as the Honda Cbr600rr or the Yamaha R6.

After doing tons of research over the past few months, most experienced riders will say that even if you've been riding dirtbikes, it is a bit different on the streets. Everyone doesn't want to have a 300. However, I think it may be good to start on a 300, learn the ways of the road on a bike that can't go 300 mph, and to max it out on its capabilities. Then, move to a supersport. Not currently able to buy a bike this moment but that is what I have found.

Personally, I just want to get a supersport and be done with it. Learn on a bike with power and respect it. But, that's not what most I've talked to with experience will say. Good luck.

Yeah I have a friend who started on an R1 and said 100% do not start on a liter bike, so I'm probably gonna just look into getting a small Ninja or something similar

Ive been riding since i was 17 ( now 21 ) I am 5'6" 150 lbs. I started out on 2002 cbr 600 f4i. Since then i have owned 4 600rr's and a 125cc grom. I am glad I did start out on a 600 rather than a 250 or 300. because its almost like driving and learning a manual car, once u can drive a manual car, you can pretty much drive anything.

A guy your size and height should do the same. Ride that for a while and maybe over time get a couple different 600cc bikes and go from there. Maybe once you're comfortable enough learning the power street bikes have, you'll decide on that 1000

They just came out with a new Ninja 400, a very nice bike. My girlfriend just got one. Worth checking out for sure.
Not as slow as the 250s, but not too much power you can't handle. And they look realllllly nice.