Beware that for sure the Midland GXT-900 and later, along with some Motorola models will not have sufficient volume to drive helmet speaker headsets at speed.
Midland once made the absolute best GMRS radio for basic Bike2Bike. Then somewhere around their 850-series they made a significant change in the maximum headset volume that prohibits the volume from being loud enough for higher motorcycle speeds. Basically you can't hear them above 30 mph, regardless of the headset used.
Right now the best model that provides good audio output is probably the Cobra Li-7200. There are a couple of helmet speaker headsets compatible with the unit.
If you are using the GMRS radio with a comm system (Starcom, J&M, Sena, etc.) the volume issue is not a problem. But if you are attempting to build a simple Bike2Bike setup using only two radios and helmet speaker headsets, make sure you know the model radio you are purchasing and what it will do.
There is a resident expert on the forum. PM "LeeDavis" for detailed info. He stays current on GMRS radios and basic headsets.