https://daringfireball.net/2008/06/iphone_3g_upgrade
Daring Fireball: The iPhone 3G Upgrade Question
So if you’ve already got an iPhone, should you buy a new iPhone 3G?
daring fireballiphone 3gupgradequestion
https://daringfireball.net/2010/07/iphone_4_3g_performance
Daring Fireball: iPhone 4 3G Data Performance
Benchmarking 3G data performance on the iPhone 4, iPhone 3GS, and iPad 3G.
daring fireballiphone 4data performance3g