I have 2 Berninas - 730 and 230 - and love them both. I've never had a problem with uneven stitches. Several ladies in our quilt guild have 440s and love them - no problems with uneven stitches. I have an automatic thread cutter but I never use it, because I like to leave longer tails at the end of my seams. My local Bernina dealer has the best customer service I've ever received for anything I've ever purchased. I've never owned a Viking because there is not a Viking dealer in my area, and I wouldn't buy a machine without sewing on it several times before buying it.
I have 2 Janomes (purchased before I got my Berninas) - 6500 and ?QE - and like them both. The bobbin winder stopped working after about one year. Machine was still under warranty but the shop repairman couldn't find what was wrong so I would have had to send it to Janome to have it repaired (shipping charges would be my expense). I didn't get it fixed - I just wind my bobbins on the other machine. My Janome walking foot doesn't work as nicely as the Bernina, but I didn't realize that until I had my first Bernina.
I've also had Kenmore sewing machines (made by Janome Company)many years ago and had no problems with them.
Be sure and sew on the machines as much as possible before you make your decision. Keep in mind that if a feature bothers you - the more often you use the machine, the more it will probably bother you.