There's only two "versions." Retail (1.23 being the latest patched version), and The Secret Files (which is numbered version 1.24 to prevent incompatibilities).

1.23 is the more popular version for online play since TSF was never released outside of a small portion of Europe, but this is moot thanks to Blur's JJ2+, which adds a ton of multiplayer features, compatibility between the two existing versions and some bugfixes. As long as you've got either of those, they can be patched to plus versions.