Hello deepak,
It is always recommended to stack switches with the same IOS levels... Even if the switches have different licenses, when it is upgraded the next time, all the switches will get the same IOS images from the master.. If you have mixture of switches, the switch with the EMI image by default becomes the master.. if you force priority on the switches and make the SMI switch as the master, the stack can lose many useful features provided by the EMI software...
Have a look at this URL for more info :
http://cisco.com/en/US/products/hw/switches/ps5023/products_white_paper09186a00801b096a.shtml#wp41055
In order to avoid all these confusions, it is best to have the same IOS in all the switches !!!!!
Hope this helps.. all the best.. rate replies if found useful..
Raj
