I have not tried the 4 needle commercial machine. After wearing out a Bernina in 3 years (I quilt a LOT), I went with Janome. I have had this one for 7 years with only regular maintenance. I was told by someone who should know that some Viking models are even made by Janome. My DH and I were really impressed with the ease of maintenance and solid construction of the machine I've got.
I may eventually get my 30 year old Viking back from my son, but these are the only 2 brands I would consider buying.