Hi teal,
I only have limited experience with the LSAT (I've taken it, but haven't spent nearly as much time with those materials), so I don't know if I have the best opinion on that front. I will say that when I've had students who run out of
OG (and
OG supplement) material, I tend to refer them to the 11th edition, then the 10th edition, then the LSAT.
From what I understand, the LSAT passages tend to have more of an argument-type structure (this makes sense given the purpose of the LSAT), and it's helpful to think of the passage in terms of that argument--what the two sides are, which side the author falls on, etc. The GMAT RC passages do not necessarily follow those guidelines. So *some* practice with those passages might help (and if you're out of materials, you're out of materials, so you have to choose from what's available!) but it's not ideal.
If you have a hard time with those abstract passages, though--sure, give those similar-type passages on a shot on the LSAT. Third-party GMAT materials are an option too--there are many opinions on the forums here about which materials written by prep companies are the materials that other students have found most useful.
To everyone out there who hasn't finished the
OG content yet (or for that matter, even if you are studying for the LSAT and may hit this same problem)-- please pace yourself with these official materials! There are not that many out there, and burning through them too quickly is an unnecessary waste. There are many strategy points to work on, and many excellent courses/books/teachers out there who can help you work on them in a way that helps squeeze the greatest value out of these questions. By way of analogy-- if you play tennis for 10,000 hours you will probably get better, but you'll also ingrain a lot of bad habits. If you play 5,000 hours, but have excellent coaching along the way, you're likely to get much more of a performance boost.