I also have a Bernina and some vintage Singers. I think the number one thing to realize is that no machine just runs along fine without some maintenance. When I only had the Bernina, it went to the shop for a tune up every year like clockwork. Now that I'm using the vintage machines to piece, I extend it out a bit to 18 months. I've also learned that using an older machine is different than using a more contemporary electronic machine. Even though my 301 is the machine I learned to sew on, I went back and reviewed the manual and read on here about it before I started using it again. Ditto with the 503 and I will do the same with the Featherweight before I start using it.
If you have switched needles, cleaned the bobbin area, rethreaded it and took the bobbin out and reinserted it, then you will probably have to take it in to be repaired. As to which one, it's really a personal decision. I love my vintage Singers for piecing, but IMO for garment construction there is nothing like my Bernina.
You can buy a bobbin case and foot pedal and replace those yourself. Neither of them requires any special knowledge. You can probably pick either of them up on eBay pretty reasonably.