Agreed, the MFF SIM makes for more reliable hardware. But surface-mount assembly is permanent. When you buy the SIM from one particular network operator, like Deutsche Telekom, you are locked in.
In theory, it should be possible to buy a 'blank' SIM, embed it in your device, and then program it with the network access credentials for any Mobile Network Operator. But as usual, commercial paranoia means that this will probably never be allowed.
Replay available now: A handful of emerging network technologies are competing to be the preferred wide-area connection for the Internet of Things. All claim lower costs and power use than cellular but none have wide deployment yet. Listen in as proponents of leading contenders make their case to be the metro or national IoT network of the future. Rick Merritt, EE Times Silicon Valley Bureau Chief, moderators this discussion. Join in and ask his guests questions.