Display: Both mobiles have Super AMOLED screen with 16M colors. S2 has a 4.3 inch screen with a resolution of 480 X 800 pixels, but Note has a 5.3 inch screen with a resolution of 800 X 1280 pixels.
Size: Note is a big and heavy device, while S2 is a light weight mobile. Note weighs 178g, while S2 just weighs 116g. Note is 146.9mm long, 83mm wide and has a depth of 9.7mm. Galaxy S2 is 125.3mm long, 66.1mm wide and has a depth of just 8.5mm.
Android Version: S2 features Android 2.3OS, while Note has its advanced version Android 2.3.5.
Processor: Both mobiles have dual core processors. S2 features a 1.2Ghz processor, while Note has 1.4Ghz Cortex A9 CPU powered by Mali 400MP GPU.
Camera: Both mobiles have 8MP camera with a resolution of 3264x2448 pixels, along with LED flash and autofocus features. Both also have a 2MP secondary camera. Both cells have touch focus, geo-tagging, image stabilization along with face and smile detection features. Both can record HD 1080p video at 30fps.
Battery: Note has a strong battery. It has a 2500mAH battery providing 26 hours of talk time on 2G and 13 hours of talk time on 3G. However, S2 has 1650mAH battery, providing 18 hours of talk time on 2G and 8 hours 40 minutes of talk time on 3G.
Storage: Both the mobiles are available with 16GB and 32GB internal storage capacity along with 1GB of RAM. Both can be expanded through microSD memory card up to 32GB.
Price: Galaxy S2 will cost around 27,500 Rs, while Galaxy Note will cost around 32,700 Rs in the market.
On an all, Note has better features than S2 but Note is a bulky and expensive smartphone which can be considered as a tablet also. So if you want light weight and less expensive smartphone, go for Galaxy S2.