Verizon remains the dominant player in the U.S. market, with the biggest 4G LTE network and the biggest footprint. After focusing on modernizing their network over the past few years and migrating to 4G LTE, They've spent a lot of 2014 building out capacity to improve network congestion in urban areas. However, you will pay for the privilege. Verizon isn't the most competitive on price, simply because they don't have to be.
One problem that Verizon has faced with the iPhone in the past is going away: simultaneous voice and data communication; namely, that iPhones on Verizon's network couldn't do it. That's changing thanks to two factors: Verizon will soon bringing online Voice over LTE (VoLTE), voice call technology that is encoded as data instead of a dedicated radio channel, and the iPhone 6 can do VoLTE. So users in the past who were worried about not being able to access the web while they were talking, or pull up map information and so on, won't need to worry going forward.