Have to be honest with you and say unless you love to tweak your phone and spend loads of time on an internet forum trying to get your phone to function the way you want you are probably better off staying away from the N900. Everyone here will tell you go for N900 but if you went to the HTC forums you can guess what they say.

For a main stream user I think this would be a no contest. HTC destroys the N900. Give the two devices to 100 average consumers to try out for a week that have no bias to HTC, Nokia, Linux or Android and I am guessing like 95 will pick the HTC.

However, the keyboard is important to you which confuses the situation. Desire Z has a keyboard but you have said that is too expensive. What of the Galaxy Epic? Is that available and affordable where you live? That has a hardware keyboard and a pretty amazing one at that, with dedicated number keys.