Personally, I would go for the Lumia, soley cuz I prefer the physical appearance, BUT here is what www.knowyourmobile.com said...
Two of the most talked about phones to be shown-off at this year's CES in Las Vegas are Nokia's Lumia 900 and Sony's Xperia S, and it's easy to see why as both devices seem to have everything the modern consumer could ask for.
In order to see which of these upcoming smartphones merits the most excitement we've decided to let them duke it out.
Power
Sony's first major release since dropping Ericsson sees the introduction of dual-core architecture in the form of a 1.5GHz dual-core CPU, which should chuck out more than enough power to have the Xperia S humming along nicely.
The device also benefits from Adreno 220 graphics, 1GB RAM and either 16 or 32GB of on-board storage space, but there's no space for micro SD expansion in the device.
Nokia's Lumia 900 carries on the tradition set be the previous two iterations of the line, which is to fit the phones with a single-core CPU with the clock speed ratcheted up to give the device the poke it needs.
The Lumia 900's CPU runs at 1.4GHz, and the device also offers 512MB RAM and 16GB of storage but, again, fails to offer expandable memory, so once you run out of gigabytes, you're out of luck, unless you take advantage of SkyDrive's 25GB of free cloud-based storage, that is.
Winner - Sony Xperia S
Display
Nokia's Lumia 900 features a 4.3-inch AMOLED touchscreen that operates at a resolution of 480x800 pixels and has a pixel density of 217ppi, which is hardly remarkable by anyone's standards.
Sony's Xperia S is much more the ticket with a 4.3-inch LED-backlit LCD screen operating at 720x1280 and with its pixel density of 342PPI, it's better than Apple's Retina Display-toting iPhone 4S.
As if that wasn't enough to get the tech-heads drooling, the Xperia S also benefits from Sony's Mobile BRAVIA Engine, which tweaks the visuals to get even more from the screen!
Winner - Sony Xperia S
Form & Build
Sony Xperia - 128 x 64 x 10.6mm, 144g
Nokia Lumia 900 - 127.8 x 68.5 x 11.5mm, 160g
Sony's Xperia S is a neat looking device which is odds-on to win the award for the world's weirdest antenna design, which takes the form of a translucent strip running along the bottom of the device.
Aside from its antennae based quirks it's pretty standard fare with a nice, slim chassis, touch sensitive controls and nice, symmetrical camera layout on the rear of the device.
Nokia's Lumia 900 is also easy on the eye. The phone is, like it's brothers, crafted from a single block of polycarbonate that takes the form of a more mature iteration of the Nokia N8, which itself was an aesthetically pleasing device.
As with the Xperia S, the Lumia 900 features touch sensitive controls on the face of the device and the layout on the rear is uncluttered and functional.
The Lumia series of devices has really seen Nokia up its game in terms of design, and we're pleased to see the Lumia 900 continue the trend. Long may it continue.