IOS – Is the 3G network used by the iPad the same as the 4G network used by the iPhone

Use mitmproxy. It's proven for this sort of thing. A while back there was some uproar about the app Path uploading the adressbook to its servers. This was what was used to discover it. The guy wrote up how he used it and that's a nice intro on how to install and use mitmproxy.

From the site :

mitmproxy is an SSL-capable man-in-the-middle HTTP proxy. It provides a console interface that allows traffic flows to be inspected and edited on the fly.

mitmdump is the command-line version of mitmproxy, with the same functionality but without the frills. Think tcpdump for HTTP. Features

• Intercept and modify HTTP traffic on the fly
• Save HTTP conversations for later replay and analysis
• Replay both HTTP clients and servers
• Make scripted changes to HTTP traffic using Python
• SSL interception certs generated on the fly

The tech specs page lists the available network features per model in more detail.

GSM model A1428: UMTS/HSPA+/DC-HSDPA (850, 900, 1900, 2100 MHz); GSM/EDGE (850, 900, 1800, 1900 MHz); LTE (Bands 4 and 17)

CDMA model A1429: CDMA EV-DO Rev. A and Rev. B (800, 1900, 2100 MHz); UMTS/HSPA+/DC-HSDPA (850, 900, 1900, 2100 MHz); GSM/EDGE (850, 900, 1800, 1900 MHz); LTE (Bands 1, 3, 5, 13, 25)

GSM model A1429: UMTS/HSPA+/DC-HSDPA (850, 900, 1900, 2100 MHz); GSM/EDGE (850, 900, 1800, 1900 MHz); LTE (Bands 1, 3, 5)

In short, the two biggest differences are the CDMA vs. the GSM models. Depending on what you get, you won't even be able to do voice calls on the other type of network.

Across the two different models with GSM antennas, it appears that the same frequencies for everything but LTE are supported, so you are likely to get 3G and GPRS support across all GSM networks if the carrier supports it.