Manalto,
I'm not a Bernina connoisseur or x-spurt, but I can tell you a bit about my wife's 930 Record. She inherited it from my cousin when she died back in 2000. My cousin had bought the machine new in the 80s and to my knowledge never had it serviced.
My wife used it from about 2004 or so till 2013 when I cleaned and lubed it. It was so packed with lint and debris under the needle plate area I do not know how it was still functioning. All the other machines I've seen that were that packed with debris quit sewing. That Bernina didn't seem to care.
They are also very strong sewing machines. My wife made a denim / fleece circle quilt with hers and the machine never missed a stitch. That quilt weighs a ton and has places with multiple layers of denim and fleece. That machine stitched right over it like it was only two layers thick. She didn't baby it either. Here's a pic of the circle quilt:
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They are very reliable. I'd say that more failures are caused by operator error, than machine defects.
They do have some plastic gears, but although that is a negative in my opinion they don't fail that often. And they are still available and can be replaced. Forum member Candace is quite good at Bernina servicing.
Because I have limited experience with Bernina's I'd suggest a 930 Record with all it's attachments and accessories. Be sure to get the owners manual as well. They can be downloaded from the Bernina site, but the OEM one is so nice to have. You'll pay a bit more for a complete ensemble, but in my opinion it's well worth it.
Joe