I'm not sure who made the comment on the "vintage sm subreddit" might be, but that makes no sense to me. I have a 401, which takes a Class 66 bobbin, a 301, that takes the same bobbin as a Featherweight, A 15-91, which takes a different bobbin and a 201-2, which takes a class 66 bobbin. Bobbins are cheap and if you sew, you aren't likely to get them mixed up.
Each of those machines have their good/great points. The 301 goes fast, plus it's fairly lightweight for classes. The 401 has built in "zig-zag" stitches and has excellent engineering. I learned to sew on a 15-91, plus it's supposed to be good for FMQ (I really am going to learn someday.). The 201-2 just hums. It's so well made that it makes little noise. I have my eyes pealed for a featherweight, but I already have those bobbins.
Therefore, I disagree with the comment on the "vintage sm subreddit". You'll miss some great machines if you follow that advice.
bkay