The Singer 301s are very prized. I have a black one and just LOVE it. I am using it much more than my modern Brother machine.
I also have a Featherweight, and just put a 66 back into a treadle. Plus a couple of others that are not useable right now, but will be eventually.
It really depends on what you like, but I certainly would NOT waste money on anything built after early 1960s, as they all went to plastic gears, etc. and are not reliable and cost more to fix than they are worth.