N900 for sure, just by comparing technical specs (eg hardware) except 12mp camera Satio sucks
besides Symbian is pretty much dead + SE financial issues go with N900 just remeber to ask advice and use search if you have issues..N900 sorta unpolished but awesome

N900, iPhone or Desire..

Satio is a nice enough s60v5 device (had mine for 4 months before I got the N900)
the SE overlay theme makes for nice kinetic scrolling and gives nice, ordered links to media, shortcuts, favourite contacts/web links etc, however, at some point you end up "under the hood" and stuck with the s60 v5 interface.
the lack of kinetic scrolling in the underlying menu screens (added to the "do i need to single or double tap to open this?" dilemna) can make for a bit of frustration. At least Nokia have made efforts to get uniformity with devices like the N97 and 5800....on this front.
Touch screen keyboard on the Satio is one of the better ones and is very responsive.
I'd say if you want a nice mediacentric device with a great camera and all the usual symbian benefits (and annoying traits) without the flexibility of being able to tweak the guts out of it, the Satio isn't a bad option, but then most of the android based devices will outshine it in performance (and available apps - if that's your thing).
If you're after a device that you can tinker with and tweak and enjoy learning about (+ you get the bonus of reading all the new threads from people whining about when the next FW release will come out ), with the bonus of having great, integrated connectivity options for networking, then the N900 is the choice for you....

ps: one BIG frustration with the Satio is SE's determination to stick with the proprietry connector for headphones..... and the location of the jack on the side fo the phone...

simple
If you are new to nokia then choose Satio if not then choose Nokia.

if you are new to noks then Satio will over indulge you with software from good old simbian...... however for old hats (most) simbian has had its day in the sun.

if you want to learn something then choose n900. be prepared though or else you will end up hating the fact that you ever bought it.

not because its rubbish (contrary to some bitter others) but because of what N900 represents and stands for. this is the fact that some while purchasing seems to forget.

CN

To be perfectly honest maemo's interface looks like they stole it from Android.

Meego sounds cool but might end up being another failed platform and I don't see Nokia making any new maemo devices there is reason why symbian so popular and is supported by so many people because Nokia no matter refuses to ditch the os.

Despite what I said maemo sounds pretty cool with its openess because we all know about that Symbian signed battleground.

Also Sony fanboy for life here won't effect my purchasing decision maybe I should wait for Sony Ericsson Meego device.

rrmaster: make sure you read all the 'problem' threads on this forum.. and there's a giant thread that lists all n900 problems for potential buyers. most of them contain the solution/workarounds, but the community don't have much sympathy for users who don't take the time to 'research' the n900 beforehand for its shortcomings.

i have an n900 which i couldn't be happier with and my wife has a satio which is finally quite a solid phone after a shaky start. the camera on the satio is outstanding but symbian is a boring and outdated o.s and while the n900 has a much worse camera everything else is far better