Size and Design:
Google Nexus S has a soap bar type of shape with edges that are completely curved. Desire on the other hand looks more stylish with nicely curved edges. Nexus S is larger of the two but much slimmer with thickness of 10.9mm in contrast to 11.7mm of Desire S. There is just one gram difference in weight between them with Nexus S weighing 129g and Desire S 130g. The attractive design of Desire S is more likely to catch the buyer’s attention.
Desire S features the S-LCD TFT capacitive touchscreen with resolution of 480 x 800 pixels and 16M color support. It has HTC sense UI and features multi-touch input method, accelerometer and proximity sensor. Nexus S has the more advanced Super AMOLED TFT touchscreen with resolution of 480 x 800 pixels and 16M color support. The Super AMOLED display is much better than S-LCD and 4.0 inch screen of Nexus S against 3.7inch display of Desire S makes it a clear winner here.
Processor and OS
Both the smart phones features the latest Android 2.3(Gingerbread) OS. Desire S has 1 GHz scorpion processor powered by Adreno 205 GPU. Nexus S features 1 GHz ARM Cortex-A8 processor with Power VR GPU. These specifications tie it out on this front.
Both phones feature 5MP auto focus camera with LED flash but Desire S has a slight advantage being able to record HD 720p video at 30fps in contrast to 30fps WVGA recording in Nexus S. Desire S also has the image stabilization feature in addition to the common geo-tagging and touch focus features in both the smart phones.
Nexus S has 16GB of internal storage and 512MB of RAM t go with it whereas Desire S has 1.1GB of ROM and 768MB of RAM. Both phones support micro SD card up to 32GB.
With both phones having very much the same features, a lot will depend upon their price and that may well be the deciding factor for the buyers. Nexus S in India is priced around RS 20,000 and Desire S in India 22500. However, My personal opinion is aligned towards HTC Desire S