Which mode should I use for InfinityAT?

VXCharts uses only mode 1 (UDP) in order to prevent your charts from lagging, however, technical support from Infinity may sometimes suggest that you switch InfinityAT to use mode 2 (TCP) instead of the original mode 1.

To use an analogy, think of

Mode 1 as a Bike, rider not well protected, but very fast and nimble.
Mode 2 as a Car, driver is well protected, but car is harder to maneuvre (thus slower than a bike).

If you have a problem with your bike (Mode 1) not working, you ought to have your bike checked and fixed.
However, if you were simply switched to driving a car (Mode 2), your bike (Mode 1) is still not fixed.

The bottom line is this:

We use Mode 1 (bike) because the price updates are fast. So, if your InfintyAT and VXCharts are not using the same mode, sooner or later, you are going to find that the prices are different, which makes it impossible to trade.

Our internal analysis indicates that InfinityAT lacks a heartbeat signal with the server, thus causing it to stop receiving data under certain circumstances (and switching to mode 2 is unlikely to resolve the issue), however this is something that only Infinity can confirm or deny (and fix).

http://en.wikipedia.org/wiki/User_Datagram_Protocol
http://en.wikipedia.org/wiki/Transmission_Control_Protocol