I have both an Edirol R-09 and the Zoom H-4 devices.

Edirol is Smaller than the H-4 but not smaller than the H2.

Two things the Edirol has over the H-4, and I assume the same with the H-2 are:

1) The Edirol stores files with a time-date stamp to enable you to keep track of the files and when they wer recorded
2) The Edirol has a recording level control which available right away. The H-4 has it buried in some menus.

The Edirol can record on SD cards up to 4G in size.   I think the Zoom has the same limit. Both are software upgradeable by downloading the proper file and loading the file onto a memory card and starting up the device in the proper way to update. Both are good. Reasonable in usage. The R-09 comes in other oolours besides black. I think the H-4 only comes in the silver/chrome plastic oolour. Please do a search in the Mudcat using Google and it'll bring up some of the other threads on the same topic.