The Designer is already obsolete; my BFF has a Diamond and it is already falling behind the times. So there is really no keeping up with the technology. If you really don't use or want the embroidery feature, I would definitely look at Janomes. I have a Babylock which I love but I do a lot of embroidery. If I were looking at something for sewing primarily, I would buy a Janome 6500 or a Horizon (skip that 6600-it's a dog!).
There is a lot to be said for being happy with your dealer so that has to play a key factor too! Good luck with your decision. (My personal opinion is to ditch the Viking and get the Janome - look at cost of accessories for Janome versus other brands!)