DUDU0001, cjd, once again thank you for your responses!

Sorry for my delayed response: I was away from technology for a couple days.

I did some tests to illustrate what I mean about light through transparency and Caustics. In this particualr one, I did get a 6s. increae in render time, but it's not always an increase. Maybe it worked this way because I have a solid transparent object, as opposed to alpha-mapped one, which seems harder for Light-through-transparency to compute.

Also, I like the shadows produced by Caustics more - the object has solidity to it, while still being transparent. It seems more like glass objects in real life.

(In both cases my light sourse has hard shaddows in this case, but you wouldn't know it from the Light-Through-Transparency image).