Clearly they are as big an advantage as using EPO, so it is complete hypocrisy to bash EPO use and not altitude tent use. And before some of you try clever replies:
1) tents are NOT the same as living at altitude. Tents let you sleep at extremely high altitude anywhere you live, and then immediately train at sea level. That is not a natural scenario.
2) breathing in synthetic air to boost your epo, is no different than injecting a synthetic substance to boost your epo. And yes, it IS synthetic air, as in rAIR.
3) they may not be illegal now, but WADA was looking very closely at banning them, and wanted to, but didn't know how to do so. In other words, this is no different than blood doping in the 70's & '80's before it was illegal, yet many cast aspersion at Viren and others for a practice that was not illegal, but certainly unnatural and an unfair advantage, just as altitude tents are.
Look, sure Paula and Ritz are great runners on their own right, but if you think both of them didn't get a ~3% advantage from these things, you are nuts. Paula is a 2:19/2:20 marathoner without the tent, and ritz is a 13:05 guy without one.
ALTITUDE TENT CHEATS OUT!