As with machines, I'd go around and try a few first. What is good for one maybe more scary for others. There are some that I've heard that are self threading but I've also heard those can be tricky. Most once a machine has been threaded right try to avoid unthreading them. Instead they tie the new thread to the already threaded thread and pull it thru. My next purchase will be a new serger but I will try several out. I have one that is over 20yrs old and its been close to that since it's been used; alot had changed since then. Nancy Zieman has videos on them and she has a book about quilting with them. I know some searge the fabric before washing.

I have had a serger for at least 20 years. My first one was a lower end Bernina and the threading was the worst part. If one of your threads break or run out you have to start over. I traded that particular model in for a more expensive one several years ago and I have never been sorry. It is much easier to thread. If something breaks or runs out you only have to rethread that one. I make at least 20 simple Linus quilts a month. I make them envelope style and use the serger to sew up the three sides of the original sandwhich and then birth it. The serger makes a sturdy seam with little bulk and is fast. I then birth the pillowcase type creation and machine quilt it using a decorative stitch and usually varigeted thread.
Over the years I have done garment sewing first for my daughter and later for my grand daughters etc. The serger is wonderful, especially for knits.

I have an older serger but I love it!!!! When I went to learn how to use it I made my own directions and used colored pens to make a diagram that I could see and understand for threading.

If money was no object I would get a self threading and with automatic tension control. Of course, I'd shop around and see which one fit my budget and me. A used one from a good dealer would be OK too. All the major brands have them now.