The Elna 740 got a bad review here:
http://sewing.patternreview.com/Sewi.../Review/1/4274
This review from the same site was better, but also mentions the extra stitches problem:
http://sewing.patternreview.com/Sewi.../Review/1/4243
There may be other reviews of both machines on that website: I only glanced at the two that showed up on the first page of my search.
My personal bias is towards Janome and away from Elna. I worked in a sewing machine dealership many years ago, and at that time the Elna machines were not as good as other brands in the shop. Since then I have noticed online that no quilters seem to rave about their beloved Elna machines, whereas lots profess love for their Janome machines. I figure there's probably a reason for that.
One thing I learned in the dealership was that flash and features do not make up for a lack of reliability. One of the reasons I love my old Bernina 1230 is because of her reliability. She does everything she was made to do beautifully, without any problems.