Your nephew will much prefer the Ninja 250 to the other bikes on your list. It's got the looks and the cool factor . . . plus it'll run 85mph if asked.
uumm... with a 6'4", 260lb rider above 5,000' in elevation it'll show over 100mph without issue. Takes a few (thousand) feet to get the last 5mph, but it'll do it. 85 (indicated at least) is a complete non-issue, WELL within the useable range.
I'm a staunch advocate for the Ninja 250.. bought one for my wife 9 years ago and we haven't gone more than a few months without one in the garage since. There's been a few times when it was the Only bike in the garage, and for more than a few months in a row too.
But dual-sport bikes are better first bikes. Easier to ride, nothing really breaks in newbie drops, cheaper to insure and if you pick well, they're more than capable of highway duty. One just needs to feel comfortable in the saddle (meaning the inseam challenged, like my wife, need not apply)