This might be well known to everyone but it wasn't to me.
Previously I have been using a garlic press when preparing garlic. When I went to Tenerife before Christmas I had a paella dish and noticed large pieces of garlic in the dish. Since then I have experimented with using different size pieces of garlic in my curries from crushed to coarsely sliced.
If you crush the garlic 2 things happen: First off it is much easier to burn when frying on it's own in oil. Secondly it imparts a much deeper garlic flavour to the dish you're cooking providing you don't burn it. I've just googled for "cooking garlic" and this does seem to be the case.
So if you want a strongly garlic flavoured curry the crushed garlic does the job for the flavour.
One other thing, close your eyes when pressing the garlic in a crusher. I got some garlic in my eye recently and it isn't good!
Paul.