I feel obligated to offer this from the onset: The HTC Titan II and Nokia Lumia 900 are both excellent Windows Phones. There's really not a bad choice between the two. One may suit your tastes better than the other but that doesn't make the one not chosen a bad Windows Phone. Having gotten that out of the way, when the two phones hit the market I found the Titan II more appealing. The larger screen and better camera gave the phone an edge over the Lumia 900. Both screens are high quality but for me, the Titan II appeared more natural and it was easier to view outdoors.
But that initial preference was based on hardware alone. After a few months on the market, a feature beyond the nuts and bolts of these two Windows Phones began to take shape making things a little more difficult to choose between the two. That feature is manufacture support.
Shortly after the Lumia 900 release Nokia set an example of product-support that should be the model for others to follow. There was a bug that dropped data connectivity on a few devices and instead of white washing things, Nokia recognized the problem and distributed a fix within a week of the Lumia 900's release. On top of quickly responding to the problem, Nokia compensated customers for their trouble with a $100 credit.