Compatibility of GSM shield

Hello, I am Karthick Ashwath , an electronics hobbyist with a not so big budget.I want to use GSM. I have two choices:

A) I could buy the Genuine Arduino shield and try to stretch my budget (It costs 140$ in India)

B)I could buy a clone shield which costs only 32$(Here's the link: http://www.ebay.in/itm/SIM-900-Quad-Band-GSM-GPRS-Shield-For-Arduino-with-Internal-Antenna-/261899723402?pt=LH_DefaultDomain_203&hash=item3cfa70a28a)

But the problem with choice B is that I do not know whether the code would be the same, would it use the same two pins for communication, etc. Are all SIM900 modules the same?

I am on a small budget so please tell me which of the to choices would be a wise decision. Thanks, KA.

But the problem with choice B is that I do not know whether the code would be the same,

The code for the two devices will be quite different. If you are comfortable coding, get the cheaper one. If not, get the Arduino one that makes the process simple.

would it use the same two pins for communication, etc.

It doesn't really matter. Communication between the Arduino and the GSM shield is via Serial (either HardwareSerial, that Serial is an instance of) or SoftwareSerial (or GSMSoftwareSerial, in the case of the Arduino shield).

Are all SIM900 modules the same?

No, but the differences should be minor, and the manufacturer should tell you what AT commands the chip supports, or doesn't.

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