In my expierence Venture has a pretty poor repuation. My last boat had a venture trailer, and it was a piece of junk. I'm not sure if that was because the previous owner just did not take of the trailer, or if was because Venture trailers are not very good. Eventually I got fed up and bought a brand new Magic Tilt trailer and was much happier.
As to torsion vs leaf springs, I believe most people prefer the torsion axles better because they last longer. However, leaf springs are cheaper, and can easily be replaced by a do it yourselfer. Where as replacing an entire torsion axel is much more of a project.