I bought my latest serger a few months ago. I was specifically looking for one with a particular feature - the coverlock stitch, so I was looking at Bernina and Pfaff machines (Pfaff was the more economical option for the coverlock, btw). But if I was simply looking for a four-thread machine, I would have bought a Janome without hesitation. HTH!
I have a Bernina serger and sewing machine. I got almost bottom of the line serger, but it works so well- I absolutely love it and I don't think I'd ever use a different one!! But that's just my (very biased!) opinion. Good luck!