I am riding a track bike that doesn't have mount for a rear brake, otherwise I would run both. I have a front brake but it's not always accessible depending on where my hands are. The brake is on the flat of my bullhorn so in heavy traffic and intersections I ride with my hands covering it and also gives me more up right heads up position in traffic. But on quieter side streets I like to be able to ride on the bar ends and use my legs to slow and stop and occasionally pedestrians, animals and cars do stupid stuff and I need to stop quickly so I'm just trying to see what my best option is when the brake is not in easy reach