i actually have two Bernina overlockers and both are used. Now when I bought the smaller of my two, I had the opportunity of going on an overlocker course, this course was an introduction to overlockers and limited to six people attending, there was a chance to go on part two of the overlocking course a few months later, but in order to do that you had to have completed part one.
Well there was a bit of a mixture of overlockers being used (we each had to take our own overlocker), and I can honestly say the noise of the non Bernina overlockers was very noticeable, very rough sounding, and from memory one was a Brother and the other a Janome My Lock. The Berninas and they were all different just purred away and yes I know they are more expensive than other overlockers.
Regarding your choice, it really all depends on your budget, which sounds quite a healthy one too, and your handling of such a machine. If you can hang on until this current Lockdown is over, you should be able to get to a dealer and have a demonstration of various brands, and then be able to test them yourself - that is important. Do you happen to have a dealer anywhere near where you live? All overlockers should arrive already threaded, some are more generous with supplying thread than others, so first and foremost it is important to learn how to rethread your machine, and a normal rule of thumb is the upper looper first, the lower looper second and then the needles. One way of effortlessly changing the threads (colours) is to cut the threads up near the top of the mast and tie on a new thread, and then gently pull the thread through, repeat until all new threads have been changed. Another good way of understanding your machine is to buy four different colours of overlocking spools, and thread these up, then you can actually see what each thread is doing and this will help you understand your own machine much better.
Regardless of what machine you end up buying, there is a super overlocker workbook that you can download, although it is for the Bernina overlockers, a lot of the instructions apply to all brands, and then steadily work through attaching samples of your work to the different pages, and if you do this with the machine threaded up with different colours this will help you. This workbook is found under My Bernina Overlocker basics Mastery Workbook - go to
www.bernina.comIt was Morgan who has already replied to this thread that originally found out about these wonderful Mastery Workbooks, and they are so well worth downloading and then following - so good luck.