I use my 'set' of 201's the most, very easy to set up and use, they're very sturdy, work well and I like the larger size.  All the machine  options work well though, I use my 15 type Jones less now though due to taking different bobbins but I like that its easy to adjust the bobbin tension for FMQ etc.  In terms of choosing between them if you can't narrow down preferences I would go by whats available, price, size, decal condition or type and what case/base you are wanting it to have.

With the 99, 66 and 15 if its for regular use I would go for a later one with the numbered tension dial and stitch length and with reverse stitch although the decals are prettier on the older ones.  Another thing is if not going for something set into a table is to get one with a base that either has or can take the little extension tables - I find these a necessity and the later ones sometimes come in bases that don't take them (another reason I don't use my Jones much).

Amazing, loved watching that and flicking through her blog.  Thank you for sharing the links.

Thats lovely, and so interesting looking.

Got this one done today.  I like how many layout options there are with it.  Thank you for the tutorials Iminei.

Was yours similar to this?  It was only connected to the socket with 3 wires not the motor directly, it has a parts number but internet search didn't help.  Glad yours is working well, I also find the knee lever a bit odd just now, I find I sit much further left than normal.

I love the shape of it and like how colourful your collection is.
Shame can't be tested, is it the switch that operates it?
I have a hand Essex miniature and always tempted when one with a motor comes up on eBay, just because it seems so odd such a small machine could have one.

I have similar issue with a knee 201k-3.  Is your black box wired to both motor and all 3 points in the socket (sorry got no electric language)?  Mine has 3 wires coming out of the socket and into the box but not to anything else.  As it's a sealed up box with gunk in it, I'm not sure it could be rewired so also wondering if necessary to reattach as it's wires are in tad worse condition than my motors and I'm going to replace those.
All the wiring diagrams, old manuals and pictures I can find of motors don't mention this box but they do make me feel more confident and taking motors apart and rewiring etc.

It's sometimes hard to resist things!
I kept forgetting I was wanting to search for a buttonholer with more templates so was glad just for the reminder.