Is the Zoom H4 as good as the H4N, apart from that the H4 can handle 16GB SD cards maximum? The H4 is a bit cheaper and I don't mind the 16GB card limitation.
Wouldn't even know where to start to list the improvements. In short, Zoom really listened to customer feedback on the H4 and delivered with the H4N. A Google search will bring up lots of comparisons.
IMHO, buying an H4 over the H4N would be a good idea only if you couldn't possibly afford the H4N.