The New Ninja 650 R looks cool, but they are not available for review yet. The Katana has never been cool to me. I dont know why there just not. Not to mention a new 750 is a bit much for any rider, not to mention a new one.
The 650 R seems like a decent first bike choice. Not overly powerful and aggressive, but still cool enough to keep for a long time. Of course all of this is speculation seince the 650 R is not out yet.
Give it some time for the reviews to come out, read the old posts about "first bike" and post any question any time.