BER - let me put it this way. When we were shopping, the dealer had me try a 1455 (which I think is larger than a 1200series??). It had the same hp but in comparison to the 451, it felt like a lawn mower. It was really nimble, and turned on a dime. However, I wanted a tractor that would easily and safely pull my hay equipment around my hilly farm. The 1455 was NOT that tractor. The turning radius is less of an issue, I think, than the size difference (unless I'm wrong about your tractor and it is larger than the 1455).
The power steering is great (although we were upgrading from a 1958 tractor without that feature!), and the FEL does not seem to to get in the way - not sure I understand your question about PS and the FEL. We've not had to, or wanted to, remove the loader, nor did I drive the tractor much without it on.
We didn't try the 461 - too much for what we needed and we didn't want to spend the extra money. Also they didn't have one for us to try. Interesting that it turns tighter, though. I haven't quite figured out when the LSD would be an easier option for traction than just putting it into 4WD.
The only thing that vibrates and annoys me is the SMV sign.