EE has largely cleaned up in RootMetrics' latest report into UK network performance, although Three scored the highest network reliability.
Its report tracked the UK's four networks during the fourth quarter of last year. EE won five out of six categories, for overall performance, network speed, mobile internet, call and text quality.
The operator was crowned the best in England, Northern Ireland and Scotland, tying with Three in Wales. EE's acquisition by BT was formally confirmed last week.
The UK's fourth biggest operator, which is currently trying to buy O2, won in the network reliability category for the first time. RootMetrics said Three's reliable mobile internet performance, coupled with strong call and text quality, put it in second place for overall performance.
However, Three finished in last place for network speed.
O2 continued to have the worst performance in the UK market, despite it moving into third place for speed and second place for both text quality and call performance.
Vodafone came in third for overall performance, but was deemed the UK's second fastest network for the second time in a row. The operator is in the midst of its Project Spring network infrastructure programme.
Scott Stonham, RootMetrics General Manager of Europe, said: “EE continues to provide the best mobile performance across the UK, but we’re seeing some of the other operators making good improvements across all the different ways we use our mobile phones. Choosing the mobile operator that’s right for you is not one-size-fits-all."