HC4U has a pretty good take on the few differences between the two tarps... As he notes, either could be modified to approximate the other with the addition of 2 or 4 tabs.....But without mod there are subtle differences and as Ed is fond of saying, "It is nice when customers have choices"... A point in which JRB and I agree.
FTR the JRB 11x10 was not concieived as Winter tarp.... Far more general purpose... The details of how it came about and how it fits with the full JRB hammock tent program are in another thread.
The only point I wish to make is that your comment that "someone said" end closure etc. is a bogus comment/reason not to consider.... either.
First, if you make the walls steeper and use an extra peg to overlap the ends either can be pretty well closed up on the ends.
But second, Single wall tents suffer badly from condensation when they are closed up or inadequately vented.... Winter condensation is a problem to be avoided.... Hence the door opening ovals serve a very important function, by design.