October 2017 - last edited December 2017
[Update 18 Dec 17 - Reddit has a very worthwhile post at this link for new players]
A great player guide made by fellow player (swtorista) detailing differences between being subscribed or not can be found on her website at the below link.
There is another great swtor wiki with charts for differences available at this link as well
Official Information on available characters slots can also be found at this Link