Here's my thoughts on your question.
You have boxed yourself into choosing one of two sewing machines, neither of which is a terrific price. I think you need to take a deep breath, step back, and think about this. Warranties on sewing machines do not go to the second owner - unless it is a dealer who offers it. The machine owner may think she can pass this warranty on, but more than likely she can't. You need to do your due diligence and try other machines. I sew on a Juki F-600 and I don't think anything can stand up to it. It is the only machine I've sewed on that does not pound fabric down the hole when starting on the edge of fabric. It has the strongest motor you will ever sew on besides a commercial machine. And the price is right. I've owned many brands of machines - Kenmore is my only machine I haven't owned. You can get great deals and buys on Ebay, but you need to know your facts. Google and call around and stop and try different machines. You won't believe how different they will feel....
Good luck and have fun
Judi