Tleong,
It is like asking what specific car(s) one should buy for commuting and weekend rides...very difficult to say,
"Hey, look at these three bikes", especially as the models offered have expanded so much for the past several years.

My initial pick(s) is to keep it at 600 CC max, though 500 CCs will walk any car up to 80 or so. I also think a naked bike
or less faired one makes more sense for a first scoot than the full faired racer style bikes; also easier on the arms and neck,
and the "naked" scoots usually provide more steering movement, lock to lock, for low speed maneuvers that novices have trouble learning.

Used is your better bet, and any year back to the start of the decade will snap your wrists, power-wise. Of course "newer" model year is
sometimes better, but unless it has been abused or sitting out in the rain, the UJMs are hard to break. My '87 Honda Hurricane 1000 is near
pristine, unbreakable and will still snap my eyeballs back in my head...

Do some perusing on this link, by model and year(s):
Total Motorcycle - Your virtual motorcycle destination

And, there are other good links on the web...find a few you like, then GOOG that specific model & year for reviews, of which you will find
many from the motorcycle mags, listed on the net.

Your tenacity in asking anyone here to respond that the Ninja 500 is a "better" beginner bike for you vs ___, is short sighted, as all you can
get here is purely anecdotal, and none of us know your skill, skills learning ability, etc.

Another idea is to find a 500cc, or less, that runs well, but may not be cosmetically perfect; sort of a messenger's special...good to learn on, if
you drop it you won't cry, and when you get "better" and/or tired of it, you won't have much dough in it and can move on to something newer.

Any of us making a bike rec'd, other than an opin, is like rec'd a wine for your dinner. I am not being a smartazz or snarky, but your request is
term paper investigatory in scope. Look, read, go look at scoots, think about it, etc.

The time is on your side, as buying a sled in fall/early winter is prime time for deals. But, I hope you get your MC license and learn how to ride
somewhere besides the Streets. An MSF course is highly rec'd. I still take one, as a refresher, every 3 yrs of so, and I consider myself a damn
good rider with 46+ years and hundreds of thousands of miles riding, all across the US, CDA, etc., in all kinds of conditions.
GL,mD