Yes, you're comparing extremely different beasts here. My own advice would be along the lines of, "do you want a tiny laptop or do you want a huge phone?"

The hardware on the n900 is quickly being overtaken by changes in technology. If you want the best "experience" using the device as a phone, you really can't go wrong with the Galaxy S2. And, with work, you can probably find Android equivalents for most of the tools available in Maemo.

If what you are looking for, however, is a tiny laptop that can also take the occasional phone call, there's still really no perfect equivalent to the N900.

BTW, if you really want something in-between the N900 and the S2, the N9 might just meet your needs...