I am a Pfaffie too. And my Pfaff is also 25 years old! -- a 7550, one of the last made in Germany Pfaffs. I pray that my machine will remain reliable forever. I don't know what I'd get if it died. I agree with those who feel it's subjective. How long is an appropriate length of string? It depends on who you ask and why you're asking ;-).
I think a machine that does the functions you need and that you feel comfortable and "bond" with because it does everything predictably for YOU is the best machine. The brand doesn't really matter.
I've seen gems and duds in every brand. And even paying more doesn't mean you'll get the best machine. Make sure and read loads of reviews before deciding.