Nothing will sew a straight stitch like a vintage machine. Featherweights are cute, easy and lightweight enough to carry to classes, and just plain fun. Handcranks are a little trickier to get used to although there are handcrank clubs in some places that require owning and using that particular machine. The sound that vintage machines make is so much different than the machines of today--a more metalic sound--that some of us find soothing. Vintage machines will usually sew much faster too. I have new machines, in fact, I just won a Janome 3160 and love it but I still use a vintage Singer a lot when I sew at home.
to clarify the first sentence: If a machine will zig zag it won't sew a perfectly straight seam. Sew a seam on your hand crank then sew one right next to it on one of your newer machines. You'll see the difference right away.