Depends on what you want for capabilities and you're likely to get as many answers as there are people on this board. My favorite machine of the 6 we currently own is my Singer model 66 from 1948 though it's straight stitch only. I just love the ease of use and quality of the stitches it makes. It's also quiet and smooth running. It's just a joy to use.
Fortunately there's no reason you need to stop at just 2.
Rodney