how cloud computing and grid computing differs on the basis of performance. say for example .. i have a local grid and a cloud service .. which one will be better to use if performance is my only criteria!! i have gone through many differences on cloud and grid computing but found nothing significant over performance issue.
P.S :- i am bit new to cloud computing
Generally speaking, cloud computing will give you slower machines, and all your data will have to go over the internet. However you can buy machines by the hour, so that for bursts of compute power you can probably afford to get a lot of machines.
If you set up your own local grid, you'll be able to decide the spec of machines that you get, and set them up how you like. However it'll be expensive to buy a ton of them if you're not using them all the time.
If you want to do the cost analysis, you can take a look at our cost calculator here (https://secure.slicify.com/Calculator.aspx) to get a rough idea how much on-demand compute power will cost from a variety of providers (full disclosure - this is a page on my site).