When I was learning my main concern wasn't engine capacity (but it was, because their fuel consumption), but height and weight. And I still agree with my past self that you should choose a bike you can flat foot from (at 5'9" it rules out many dual sports for me). This is why I mentioned the F650GS (and because I know it's capable of a decent FE).
A 'strom really feels like a mother ship, though
The 650 is not too heavy, not very tall, but it's still BIG.
But I have nothing against 250s - if they meet the first criterion. They won't probably fail at handling and weight
