Which Nakamichi to choose?

uberwaltz, if the same recording sounds as good on your Nak as it does on your Nottingham, something is not quite right. There are a few possibilities.
I have the same turntable, better Nak, top tape and probably better cables, and it does not overall sound as good as the turntable, though the tape is more coherent and smooth. Biggest differences are dynamics and soundstage - Nak cannot compete, though it does both quite well, for a cassette. You really need good open reel deck to compete with your Nottingham. I would also suggest trying fuller sounding cables, Nordost is not famous for that.

I had cassettes in the "old" days and if I used dolby the highs were gone and if I didn't there was tape hiss. I wouldn't go back. As far as cd's and vinyl, the only formats I run other than streaming, some are good quality and some not so much. I would hesitate to say any one format was better than another.

There is more than just losing highs with dolby - sound loses fullness. Tape hiss is inevitable but can be minimized, you do need excellent deck and tapes for that. Besides, almost all older recordings have tape hiss to various degree.

Cassettes were never the subject of the loudness wars, like CDs and vinyl. For that reason the dynamics on the humble cassette can be quite surprising. Tape is a natural medium. It breathes.

I have been listening to the Sony Cassette deck all morning, and I discovered that it has a beguiling quality, that wouldn't let me turn it off; especially when I quit comparing it to my other sources.

Maybe that's the key to the cassette; just quit comparing and enjoy.