If you don't use Superfly, it's probably not worth the upgrade just yet. (I prefer Firefly myself. I upgraded, and I don't regret it, but I still mostly use Poser 11. Because of the Python issue. If you do upgrade, you'll want to keep your old version of Poser, too.)

I think Poser 12 is, at least for now, mostly an attempt to get a program that hasn't really been updated for years on track. In particular, Python 2 reached its end of life, and had to be replaced. That's why the old scripts don't work any more.

Superfly does render much faster in Poser 12, and there's a denoiser (a common complaint with Superfly in Poser 11 is how slow it is, and how noisy the renders look). But if you don't use Superfly, you won't see those benefits.

Like you, I prefer a comic or illustrative style to photorealism. I hope future versions of Poser make comic style renders easier and more customizable.