EE, it seems, is the best all-around mobile network in the UK, winning in most of RootMetric's performance tests. It was only in call handling that it was beaten by both Vodafone and Three. EE was the overall winner, Three came second, Vodafone third and O2 last. Although O2 is likely to be disappointed, the BBC also points out that it has the smallest portion of the UK radio spectrum to work with, and a large customer base.
EE, on the other hand, is a single operator with 45% of the UK's spectrum at its disposal. This is largely thanks to heavy investment and then subsequent purchase by BT which had its own portion of the spectrum. As such Ofcom has forbidden EE to buy more in the upcoming 2.3GHz auction.
RootMetrics says that EE's call reliability issues may stem from the move to Voice over LTE (VoLTE). This system puts voice calls over the data network, rather than using a dedicated circuit for each call. It allows for much more efficient use of the network but is a newer technology that has some teething troubles. The advantages to VoLTE include better call quality and faster connections, but it also means EE has to switch to 3G seamlessly if you move out of 4G coverage.
For people who care more about data than voice or text messaging - and seriously, who gives a flying hoot about SMS these days - then EE remains a solid choice with its ultra-fast 4G network. Vodafone customers will be pleased with second place, Three users (like this writer) will be astonished that the network came in third here and O2 users will like try and go on Twitter to complain, but not be able to as it came dead last.