The difference is in the prototype.
If that level of detail is important to you, and you have a specific subject in mind, study photos to see which you need.
Single pin track is pin-link-pin-link..
Double pin track is pin-pin-link-pin-pin-link...
So whichever is more difficult is subordinate to whether that level of accuracy is important.
Bear in mind that the different types probably need different drive sprockets, so make sure that the track sets come with their sprockets, or see what the basic kit has.
Workable track means that it's like a watch band once assembled, flexible. Otherwise there are varieties of track like link-and-length that glue together in rigid sections.
Here I will give my opinion, only. There are several types of track systems on the real thing. Some AFV's have self tensioning track so there is no sag. Others have track sag, either between the return rollers such as on a Panzer 4, or one big sag such as on a T-55.
Other, primarily US tanks like the M-60; have no sag.
No sag- if link and length is available, it's simpler.
Tankskis- I like individual link.