What is the difference regarding the ability to comprehend information and put it to use? What would the symptoms be of someone with high IQ but average working memory, or someone with high working memory but average IQ?
A really good example of a high working memory but a low IQ is Kim Peek (the savant who greatly inspired Dustin Hoffman’s Rain Man). Parts of his brain didn’t work right (he was born with macrocephaly and probably had FG syndrome, according to wikipedia, and his corpus callosum hadn’t formed properly) and basically the parts of his brain that broke things down into understandable chunks weren’t working right. This gave him an amazing memory but only a little understanding. He had difficulty with abstract concepts and couldn’t understand metaphors. He had great difficulty with social situations and coped more with memorized techniques than actual social understanding.
On the other hand, he memorized the Bible, the complete works of Shakespeare as well as every Reader’s Digest condense book available to him, and he did things like read through the telephone book to add up the numbers in his head. He is said to have remembered 98% of everything that he read, and could accurately recall the contents of over 12,000 books. He memorized zip codes and the maps in phone books, and could give directions within any major city in the U.S. His abilities to instantly recall obscure facts and perform mathematical calculations earned him the nickname Kim-puter. While he could perform certain types of mathematical functions in his head (like easily adding up telephone numbers in the phone book), he could not reason through math problems.
Well, are you looking for anecdotes? I’m a member of Mensa, but have average if not sub-average working memory. Result - really good at things that require understanding a complicated concept; really bad at things that require lots of memorization. So my kids kicked my ass at the card game concentration! Among other problems! 
The difference between working memory and IQ is not only that they are totally different things, but totally different sorts of thing. This question is a bit like asking what is the difference between a car’s camshaft and its horsepower.
Furthermore, “working memory” is a technical, theoretical concept in cognitive psychology, and does not all mean the same thing as “memory” in the layman’s sense, as engineer_comp_geek seems to think. Being able to memorize lots of stuff is not an attribute of working memory but of the quite distinct faculty of long term memory (I rather think that ability at the game Concentration has to do neither with working memory or with long term memory but with intermediate term memory, which some psychologists have hypothesized as being a capacity distinct distinct from both working memory and* long term memory*, but has been less thoroughly researched and is less well established as a theoretical concept.)
Incidentally, there are no known capacity limits to human long term memory (they probably exist, but no-one has succeeded in finding them yet). The difference between someone like Kim Peek and the rest of us probably has much more to do with motivation than with actual differences in memory ability. We could all learn the works of Shakespeare and The Bible and the phone book off by heart if we really wanted to, but it wold be a lot of work and most of us have no desire to do it.
Working memory is roughly equivalent,conceptually, to what psychologists also call short term memory, the “short term” here meaning a few seconds at most, and it refers to the mental “store” in which items are held briefly in consciousness before either being forgotten or transferred to long term memory, and in which these items can actually be “thought about”, compared, and so forth. Individuals do seem to differ a little bit in how many items they can hold in working memory at a time (though nobody can manage more than a very small handful, no more than about 9) and in how long an item can remain in working memory unattended until it is forgotten (though no-one will be able to manage more than a few seconds). These parameters of working memory do affect reasoning power in some circumstances. For instance, if one sets aside differences in the learned “tricks” and heuristics that people use in real life, and have major effects on their actual performance, a person with a high working memory capacity could probably do mental arithmetic better than someone with a lower capacity. This probably factors into IQ in the same sense that the design and quality of engine components factor into the effective horsepower of a car, but is a long way,from being “the same thing as” IQ, or even really comparable to it in any meaningful way.
I can’t think of a good distinction between “comprehending” information and “putting it to use,” since I would say the definitive test of whether you have comprehended something is whether you can put it to use.
It’s possible to re-interpret your question as being about the distinction between memorizing information and making use of it, which is essentially the difference between a computer (which has faultless and enormous memory) and a human brain, which can make use of information, and indeed specializes in drawing conclusions from incomplete and inconsistent information. Among humans, at one extreme you’d have the idiot savant with the eidetic memory but an inability to say “please” and “thank you” at the right times, and at the other a very smart person with Korsakov’s.
Or you could be asking about the different ways people have of recollecting specific information. Few people actually simply memorize information the way a computer does, stashing it away bit by bit. There is always a fair amount of “compression” that goes on, in which key things are stashed away, and the rest is reconstructed when needed based on logical (or experienced) deduction from the key things. Even visual memory works this way: you do not memorize an image of a person, say, bit by bit, but instead memorize certain key distances, deviations from standard shapes and colors, et cetera, and then your visual cortex reconstructs the image from the key information using its experience of what a face “should” look like. This is the origin of many famous optical tricks. like the gorilla walking through the crowd of people playing ball trick.
But people vary significantly in how much reconstruction is easy and comfortable, and therefore what kind of trade-off they’re going to make in terms of compression versus amount to be stashed away. My general impression is that the smarter and more experienced you are, the more compression you employ – the more you’re willing to reconstruct when you need the information. For example, a physics student may simply memorize formulae. A physics professor will memorize general principles, and rapidly re-derive formulae as needed, starting from the principles. Hence the general preference, for more intelligent people, of highly heirarchical systems of thought, with basic principles leading to more complex but highly related methods of application, which in turn lead to applications. Often intelligent and experienced people look down on less heirarchical methods of learning – “Sure, he can solve the problem, but does he understand the principle? If not, he doesn’t really know what he’s doing…” But I don’t think is generally justified. It’s mistaking a preference for a particular type of learning for the only type of learning there is.