Mechanically, I don't think you have to worry about any major quality difference between 8 and 9 speeds. If it was a difference between an 8 and 10 speed, that's another story(10 speeds use a narrower chain). If you want more gears, I say go for the 9 speed.
I don't own a swift, so can't really give an answer about the second question, other than to say if you plan on taking the handlebars apart on a regular bases, it sounds like the quick release might be better.
I'm sure you'll get better advice about the quick release from other Swift owners,