I'm answering this based on OT meaning 'old toon' and NT meaning 'new toon'....cuz I think that's what you mean.

Yeah, I think maybe more people find themselves sympathetic with the NT Turtles because they are more dimensional, and more rounded out as far as the TMNT characters go. The stories allow them to show more depth as individuals. I find that I can feel more, and relate more easily to them because more is being shown how they feel and react to things. And while this may sound odd, I don't know, maybe it doesn't, I find that the way they view things, and their comments, are very much the way I think or do things.
When they came into my life, full bore, via the comic, I was already in my 30's. So it wasn't like I was unduly being influenced by them. But I admit, it sure was nice to meet some characters that sounded so familiar and made me laugh.
Which brings me to the OT Turtles.
There was sympathy and relation there too.
And actually, if it hadn't of been for that commercial catching my attention......ugh...what a thought if I had missed that.....I would have missed watching the show and then getting into the comics. Let it be said I feel I owe it to the OT show.
As far as that show went, I really liked the OT version for it's nuttball humor. And the Turtles way they played off each other. I found them endearing. They reminded me of people I knew. Mike's voice is what got me to look at the screen. I'm originally from Orange County,CA and I have friends that surf.....

my perspective of things probably isn't helping you explore the pros and cons, or what makes fans tic when it comes to OT vesus NT, is it, Sage?
Truth is, I honestly do not see much difference between the OT and NT because I tend to see TMNT as a whole. The different versions only show varying degrees of what is each of the Turtles, and the core of them remains the same.
Leo tends to be the one assigned to leadership.
Don tends to be the one to rationalize things.
Raph tends to be the one to initiate things.....sometimes without Leo's blessing.
Mike tends to be the one that finds humor in most everything......
And all the t.v. shows (and movies, books, fan-fic) either expand or play down these traits. And....sometimes we even get some uncharacteristic behavior thrown in. Because that is a possible something and the Turtles are not impervious.
Mike is the one that seems to go from OT to NT the most unchanged, but I think he is more rounded out from OT version....it's just not as noticeable maybe because he talks and jokes so much and distracts one from it.
Mike is something of a watchdog really. He often is sitting off to the side, or is pictured in the background, and he may have his mouth going. But more often than not, he's the one that's the first to see trouble coming and warn his brothers. He's not that much of a goof. What he really is, is a lesson in 'don't judge a book by it's cover'. But most people seem to miss that point.
And you know.....the more I think about it, I think Mikey prefers it that way.

I think there's another fox in the room besides me.