I heard the 3.4 is more reliable then the 2.7. On this board itself there is a thread about "hard knock" coming from a lot of 2.7s. Many people with 2.7s think there could be a recall from the hard knock or pining so many of them get. So many people complaining about the metalic pinging sound is what drove me to get the 3.4. Also, a 30% power increase is great, and they do not make a supercharger for the 2.7 so you don't have the option for that particular upgrade.

p.s. I think all Toyota vehicels are great no matter what the engine size is.