Hi Kevin,
I have never seen a Morehouse Ruth, so can offer no opinion there. As for Standard Biscuit, I have only seen three, and only that number have been graded by PSA and SGC- the two you show and an SGC 40. You are correct in identifying the two (the SGC 40 is from the earlier m101-5 also).
There are stock and a couple of production identifiers that help differentiate the two. With Standard Biscuit the creamier or more golden-looking stock, particularly noticeable on the back, is very seldom found on m101-4 cards. Standard Biscuit was likely the first advertiser to receive m101-5 or D350-1 cards, and the stock is easily seen as non-white, although it can vary in degree.
Ruth cards from m101-5 usually have that print flaw most have observed-- a line from the right border that extends toward anywhere from about his left elbow in some cards to around the sleeve of his undershirt in others. It too varies in degree, and is hard to see in your scan but is there. M101-4s will not show that line.
Many m101-4s with department store advertising (and some blanks) have print pressure lines running horizontally about 40% from the top and/or vertically 15% from the right edge, starting at the bottom. Your PSA 4 Ruth scan shows the vertical line-- it runs from the bottom of the card up through his lifted ankle. Here is a blank-backed Ruth that shows a more pronounced line:
This is another sign that it lines up with m101-4, and although this "flaw" is not found in all cards from that latter set, it is not seen in m101-5. Along with the whiter stock, it is pretty safe to say the PSA 4 Standard Biscuit is from the m101-4 set.
As for the size/dimensions of the different Standard Biscuits, I do not believe we have enough of a sample size to say that one is taller or wider than the other. In general this is not apparent for m101-5 vs m101-4 or Standard Biscuit cards overall.