A survey released this morning from the mobile ad exchange company Mobclix reveals that users of the Verizon iPhone use Wi-Fi less often than users of the AT&T iPhone. Also revealed in the study, Mobclix’s data suggests that larger metropolitan cities have a higher amount of iPhone usage over the AT&T iPhone.

According to the graph published by Mobclix, the largest areas of Verizon iPhone usage include Seattle, Chicago, New York City, Boston, and Los Angeles. This is due to the common assumption that AT&T has signal problems in large dense cities.

In its report Mobclix also reports that AT&T iPhone users use Wi-Fi about 53% of the time and Verizon users use their Wi-Fi 38% of the time. The only explanation of this is the reception problem with AT&T. Users get so fed up with dropped signal that they find the nearest open Wi-Fi point and continue with what they are doing. Granted, this isn’t an optimal way to use an iPhone and you can’t make calles over Wi-Fi but for most users they seem pretty happy about it.

Note that AT&T has a vast Wi-Fi hotspot network with over 24,000 hotspots throughout the U.S., and with the iPhone supporting auto-authentication, these points are easy to pick up and connect to when traveling or on-the-go. Another bonus to throw in is that none of the Wi-Fi usage counts towards the monthly data usage plan.

The best part about this graph is the number of users who paid the $325 early termination fee to switch to the Verizon iPhone. 2 in 3 users paid that fee with the reasons being all the same and talked about reception issues and the Personal Hotspot feature.

Mobclix mentions that 14% of iPhone 4 users are on the Verizon Network and account for 4% of total iPhone users, which is pretty good for only being on the Verizon network for a month.