There's threads on that, too.
I only have limited experience with these engines, having recently moved up from smaller airplanes. By reputation, the LA 46 is a far easier engine to handle, and more versatile. The LA 40, by contrast, has a reputation for being difficult to get a decent run out of.
Personally, I have an LA 46 and an LA 40 that has been re-timed. Of the two, the LA 46 has more power and is easier to handle. They're both on 500 square inch planes.
Controversy swirls around the LA 40 -- some feel it's a fine engine, some feel it's useless, some feel it's only good once it's been retimed, etc. Pretty much everyone agrees that the LA 46 is great right out of the box.