Regarding the question at hand, it really depends on you and your preference. If you just want a smartphone to make calls, message, email, simple web browsing, gaming etc. the SGS2 would probably be the better choice right now. As many people have pointed out, the N900 is more like a mini computer/internet tablet that can make calls rather than simply a smartphone.

Personally, I would never swap my N900 for an SGS2 as long as it still works, and I use mine daily as a phone too. I can also understand long time Maemo users searching for N900s to replace broken/lost ones, there simply isn't anything quite like it currently, including the N9 which is more of a conventional smartphone.

But for new users or those less familiar with the N900 and Maemo, who don't really need its unique capabilities, openness and versatility, and who primarily want just a smartphone, they may be better off getting an SGS2 or another leading smartphone. The Galaxy Nexus looks pretty cool, but it's pretty obvious Samsung has cut back some of the hardware features to implement in a SGS3 next year. In some aspects (screen technology, graphics GPU) the Galaxy Nexus is beaten by the GS2!