The comparison site collected data from more than 32,000 speed tests run by mobile broadband users over the past 11 months. As well as being named best overall mobile provider, 3 also came top in the Best Value for Money and Customer Satisfaction categories.
"3 represent good value for money for those happy to commit to an 18 month contract with their aggressively priced £7.87 per month offer and have competitive deals on mobile broadband contracts with 'free' laptops," said Broadband Expert.
O2 was named the mobile provider with the fastest mobile broadband, with an average download speed of 2.88Mbps, while T-Mobile came last when it came to average download speed.
According to Broadband Expert spokesperson Rob Webber: "while there is a clear disparity between average speeds it is encouraging to see that all providers now average around or above the 2Mbps mark."
Vodafone was named as the mobile broadband provider with the most consistent coverage throughout the UK.
"Broadband Expert receives more complaints and comments from mobile broadband users about coverage - or poor speeds in areas of low coverage - than in any other area; however Vodafone have received less negative feedback from users than other mobile networks," Webber said.
"Networks have different levels of coverage dependent on where you are in the UK. It is advised that consumers use a coverage checker before deciding on a provider as the best network in one area could have the poorest coverage in another area."