The 2500's and 8500's are the ones for me (with a slight edge to the 8500 as you're factoring in the ceramic bezels, upgraded movements, exhibition caseback, and slightly better bracelets/straps). I also prefer the larger crowns and He release on the 8500. It just looks a bit more proportional to me.
The 2500 on bracelet was my first (good lord that's a great tool watch), followed by an 8500 Ti on bracelet, then the 8501 Ceragold, the Deep Black next and I recently added the stainless 8500 a few months back. I'm not sure I'd be able to part with any of them. They're all classics to me! (all in the 45.5mm case size).
It's the brand new PO's that I'm not really a big fan of with the exception of the Deep Black. The "hash-marks" on the bezel don't really do it for me and they seem to contrast too much on most models. To be fair I haven't played with many in person so I'm sure that opinion will change eventually.
For now I have to go with my 45.5mm Ceragold being my favourite!