I own 2 Singers, Elna, Juki and a Hobbylock. I also had a White. The White was a bear to thread so I sold it. I really like the Elna but it does require more frequent oiling than the others.
I bought my first serger, a singer, at Sears. They let me sit down at it, watch the video, thread it, and sew on it. My biggest concern was the ease of threading. All my questions were answered and I bought it, it's still going strong after 20 years and I've never had to take it in for servicing.
So if you can demo it first, that would probably be your best indicator.