So now thats its official that Verizon will have the iPhone 4 in February, should you switch? If your an iPhone user now (on AT&T of course) you might be thinking about switching. Here is what you should consider first...
First, the difference in the networks.
AT&T uses the GSM Network. This is the technology used by the phone to communicate with the towers. GSM is a what almost the whole world uses (aside from the U.S. which has two primary network types). The advantage of the GSM network is if you travel outside the U.S. you can still use your phone. You need to contact AT&T and pay for a little extra service plan while traveling but you can do it. Also with GSM network you can talk and use data (get email, surf the web) at the same time.
Verizon uses CDMA which is mainly a U.S. network type. Verizon does have the better coverage across the country but you can not talk and use data at the same time. If you travel abroad, you will not be able to use any Verizon phone (Except for a few "world" model phones, but not the iPhone). Speed wise, AT&Ts is technically a bit faster than Verizon but you probably wont notice it and since its better to have more coverage and a signal when you need it, Verizon is the better network overall.
Phones.
The way the AT&T and Verizon iPhone 4 works is identical. The only difference is an added feature on the Verizon iPhone is WiFi tethering. This is a great feature if you have a laptop, or a WiFi only iPad. You can connect any WiFi device like a laptop to the phone. Just like you would turn on your laptop and connect it to your home or work's WiFi network, it would see the iPhone and connect to it allowing you to use your cellphones connection to access the internet.
Surprisingly, the unconfirmed word is that Verizon won't charge anything extra for this feature. Normally there is an additional charge and limit to the amount of data you can use through tethering (I pay $20 for 2 Gigabytes per month on my Verizon Droid for this feature)
Who should switch.
If you always wanted an iPhone and your current phone contract is up and you get a good Verizon signal in your area (most people do) then its time to switch.
If your with AT&T and your contract is up and you hate the AT&T dropped calls and bad reception, switch.
If you are under contract with AT&T but just cant stand them anymore and are willing to pay the $100-$300 (depending on your contract) termination fee to finally get away from their horrible service, switch.
If the WiFi tethering a feature you have wanted and need, and dont want to by an extra Device (sold by Verizon or Virgin Mobile) to do this, switch.
Who should not switch.
If your happy with your current AT&T service and dont seem to have the problems most people do with dropped calls and bad signal, then just stay with what you have.
If your under contract with either AT&T or even Verizon with different phone, and dont want to pay termination fees then wait.
Here is the other thing to consider and I cant help you with this one...Apple usually announcing a new iPhone in a few months. Thats the way its been each year for 3 years now. Verizon is coming out with the iPhone 4 in February but there is no way to know if Apple will announce an iPhone 5 a few months later. If you get a new iPhone 4 now you will be locked into a two year contract and might kick yourself if a few months if the iPhone 5 comes out. There is nothing wrong with getting an iPhone 4 now if you really really want one. But if your like me and always want the newest technology, you might better off waiting a few months and seeing what happens.
The other possibility is that tons of people will switch from AT&T to Verizon thereby reducing the amount of traffic on AT&T's network, improving the signal and call quality, but this remains to be seen.