I'm in the middle of implementing deferred shading in an engine I'm working on, and now I have to make a decision on whether to use a full RGB32F texture to store positions, or reconstruct it from the depth buffer. So it's basically a RGB32F texel fetch vs a matrix vector multiplication in the fragment shader. Also the trade between memory and extra ALU operations.
Please direct me to useful resources and tell me your own experience with the subject.
In my opinion it is preferable to recalculate the position from depth. This is what I do in my deferred engine. The recalculation is a fast enough to not even show up when I've been profiling the render loop. And that (virtually no performance impact) compared to ~24MB of extra video memory usage (for a 1920x1080 texture) was an easy choice for me.