With Singer you need to say Singer before ....date and after...Old mechanical Singers were good machines. Then came the change in parts (plastic, yuk) and Singer was just never the same after that.
Kenmores are the same thing. They are always manufactured for Kenmore by someone else. Who makes what depends on the year. Takes a little research.
Even the "good" brands can have a real dog on occasion. That is where your relationship with your dealer is important. I list dealer/warranty high on my list of must haves (I find a dealer with a great service record and then look at the machines. Saves heartache in the long run.)
I walked away from a dealer who represented OK machines because they didn't know how to make a buttonhole with the one they wanted me to buy. I had to teach THEM how to make the buttonhole. They were sure the machine was broken. To me, that is a sure indicator that this was not the person I was going to go to for any problems I might have on a machine later on (it had been on the market for a while so there was really no excuse).