tbolen, don't fall for the demonstrations, or even anyone's subjective opinion. When considering the glass performance, the U value and Shgc ratings will tell you all that you need to know. You want the u-value as low as possible, and the shgc is climate specific so it depends where you are located. You should also look at the structural ratings of the full window assembly including air infiltration and design pressure. Those 4 ratings are all independently tested, and will tell you how the window will ACTUALLY perform, and be an excellent indicator of quality as well... The companies that spend 2-3 hrs talking about bells and whistles rather than the actual ratings typically do so to distract you from the fact that they do not perform well in those areas.