I think they recommend you remove the blue wire from the connector and take it off the vehicle completely if you plan on using an igniter. The reason being, your ez start will still apply power to the wire and if it hits something metal it could spark and possible damage something. You could wrap the metal end in electrical tape to prevent that, if you're not comfortable with removing it.
I just recently switch to using an igniter on my Revo because my battery in my ez start was low and was having trouble turning over the motor. I noticed a huge improvement in the ability and ease to start the engine with an igniter. It seems like the glow plug puts a big strain on the ez start batteries. It does make for an extra thing to carry, but with the ease in starting, it's worth it to me.