I own both and choose my AR over the TR-8 every jam. Tr-8 is quick and sounds good in the mix right away. The AR is one of those deep holes where I find a lot more fascination. It takes some tinkering around to get the kits dialed as you’d want them, and I love that process. I’ve got samples of all the tr-8 kits (the samples I wanted, that is) in the Rytm, so I’m not missing anything sonically either, if I want those sounds. The pads and chromatic mode are a great way to play in drum parts, performance macros built by you however you want them, scenes… all are way cooler than the scatter button.
My vote is for the analog Rytm .
Tr-8 = surface-level depth and quick to get going.
AR = well-below-surface-level depth. A hole that makes you want to dig around and explore.