Visible light transmittance for 272 is 72% in a dual pane or IG configuration, and VLT for 270 is 70% in an IG. Looking at the previous picture that I posted earlier in the thread (from the Cardinal website), it does appear that 270 is just slightly darker than 272, which does make sense. Dual-silver coatings tend toward purple rather than green and IMO 270 trends slightly less purple than 272. But once again, very few people can detect a dual silver coatings (270, 272). It is FAR more common for people to ask if their window has a coating when it's a dual silver, than for people to say that they can see it.
If it's a single silver coating like LoE-180, then virtually no one can tell it's there versus clear glass simply by looking. VT for two lites of clear glass is 82%, LoE-180 is 79% and it's very color neutral.
I posted the latest pictures to illustrate the differences in coating appearance between different Cardinal coatings viewed with specific and (reasonably) identical lighting and background. Also those units were constructed in a manner that slightly enhances coating color versus a standard IG. I wouldn't want to suggest that they are exactly what would be seen when installed in a home where lighting and background would be major contributor to what it looks like as well.
Also, while we are primarily looking at Cardinal coatings, there are other companies that coat glass for residential applications besides Cardinal, but they are all similar in that dual-silver coatings still tend toward purple and triple layer to green, with variations such as the difference between 272 and 270 shown here. Some are more neutral than others and may have slightly different performance characteristics. In fact, Cardinal's 366 is generally less green than most of the other similar-performance triple-silver options available.
Q