GSM is a very straight forward standard, whereas, CDMA is somewhat complicated. The key difference between the two is that GSM is a standard and CDMA is a technology, but GSM has attained some technology status over the years. Both GSM and CDMA technologies have pros and cons but GSM is more better.The biggest downside associated with CDMA support is its insufficient reach, particularly inside the EU market. This is the area in which GSM connectivity is dominant. While CDMA support is common in many areas of the United States and a lot of countries in Asia, GSM is common with Western Europe. The actual primary technological know-how utilized by GSM is Time Division Multiple Access. European Union and Asia have the maximum variety of Wi-Fi users. Consequently, GSM, that’s majorly easily obtainable in most of these parts, became the leader when it comes to cellular technology.GSM the first thing that should be mentioned is its huge popularity. Today, there are more than 450,000,000 subscribers all over the world. Unlike CDMA, this technology does offer the service of international roaming and that makes it highly preferred among users. GSM provides a secure network with a host of strong capabilities.GSM-enabled phones function with the use of a SIM card, which allows users the flexibility to conveniently store data and change phones at any time.Sometimes GSM enabled mobile will be locked to an particular GSM carrier.User has option to select handset of his choice ,sometime it will locked with a particular GSM network contract in a particular periods, When you buy a phone through GSM sim, chances are it comes locked to that GSM carrier’s network. This usually is not a big deal, but if you plan on doing some traveling, or you decide to switch to another carrier before your contract is up, you will probably want your phone to be able to work on different GSM networks you can do it by unlock the mobile with the GSM sim network by getting the unlocking service by software or by an online provider like MobileUnlockSolutions.com