Others have raised valid points regarding the difference between the two cards, so I won't repeat them.
One thing though; you said "from" the US. Does that mean your brother is in India and is sending for the camera from the US ? If so, why not buy the card in Mumbai ? JJ Mehta sells a normal 2GB SD card for 499/- and an Extreme III for 1299/-; and they're probably cheaper in smaller shops.
Also, the Canon SX100IS is a nice camera and though I have not used this model myself, I've read good reviews about it. However, the flash is rather weak (short range) and the flash cycling time is very long, taking more than 10 seconds between shots. I suggest your brother should keep this in mind when making his choice of camera.