It's hard to compare them, because each has a different functions (some are almost same, but the main functions are not). Anyway, I'm mainly for Airio. The in-game statistics are very detailed and useful and it's a very nice tool to auto-control your server. With some more modifications it could be used as a successor of old good CTRA. The upcoming FOX Championship organized by the Sonicrealms Racing has very close to it. At least I think so, but since I don't know how it really is, I can be wrong.
About the LFS Lapper. I believe it's useful, but since it's most used as a drift points counter on a drift servers (drift servers with lfs lapper aren't usually too favourite), I really hate it. Drifting is not about receiving points, it's about your line, speed, angle and so on.
EGT RA is a good option for races with safety car, endurace races etc. Any race where is needed the safety car or also speed limit checker or the others functions...
I'm for LFSLapper as even an idiot like me has managed to add items to the default script to enrich the racing experience (drift meter/leaderboard/yellow flag/winner flag/marshalls, etc).