The Hitachi class 385 electric trains travelled the equivalent of more than three-and-a-half times round the world between breakdowns - or 89,438 miles - in December.
The 70 trains also operate on other lines including two secondary routes between the cities, and to Dunblane, North Berwick and Lanark.
Modern Railways magazine, which compiled the figures, said they had averaged 21,617 miles between causing a delay of three minutes or more since being introduced in 2018.
Transport Scotland said they were on course to meet their 30,000-mile 2019-20 target by March.
The trains are due to run in Scotland for 25 years.
They beat new trains by manufacturers Siemens, Bombardier, CAF of Spain, and Stadler of Switzerland running in England.
The top performance followed delays to the trains’ introduction due to production problems at Hitachi’s factory in England and drivers’ windscreens having to be replaced.
Modern Railways industry and technology editor Roger Ford said: “ScotRail’s class 385 fleet has been steadily pulling away from the other 20 new fleets, and in the last couple of months reliability has been keeping pace with the best trains anywhere on the network.
“Rankings in the table are based on the average reliability over the past 12 months.
“At this rate of improvement, the class 385s will soon have earned promotion from the new trains league, competing with more established rolling stock throughout Britain.”
ScotRail engineering director Syeda Ghufran said: “It is fantastic news for Scotland’s Railway, and most importantly for our customers, that we now operate the best performing train in its class in Britain.”