The Terra is overpriced for what you get. They want you to see the name and think you're getting German glass (and pay accordingly), when they're really giving you Phillipine glass. I almost fell for it when I first heard about them, since prior to that Zeiss only put out high quality glass. I'm glad I researched (and looked through one with a critical eye) before I bought.
Of course the various Vortex Viper lines and the Diamondback are Phillipine glass too. Which is fine, as long as you aren't expecting Japanese, U.S., German, or Austrian glass.
I would take that money and get a Leupold VX3 if I were you.
Jeez, the things people put on the Internet... the tube diameter of a scope has nothing to do with the level of magnification you get. That is all in the lenses. The only advantages a larger diameter tube has are that they can be built thicker/stronger while still having room for the internal components; and that it is possible to fit an erector assembly with more elevation adjustment inside a larger tube.