Plugging along
You will find that there are several long plugs that will fit the traxxas 2.5 or 3.3. most other brands hve coded TRX for the long plug. Why? well if you want extra power from your engine and you are racing you will likely know about the firing before top dead center. Most manufacturers have several plugs which will provide a different output to the same engine. This depends on the fuel type, tuning and optimal running temperature of you engine. When you are more familiar with your vehicle you can play around with different plugs to find out which one gives your vehicle better performance.
There are too many variable to write anything more about it here, but if you are into racing and tweaking the performnce band so you dont stress your engine then there is this book that can help you a bit.
Ultimate Nitro Tuning Handbook. 2ed. 2006.