Answer : That would depend on what you mean by "BEST". I once saw a Canadian window at a trade show, the Arctic Shield (?) that was a triple pane low e with krypton gas fill. The Vinyl frame was 10 inches wide with a wood core. It had an incredibly low U factor something like a .12 or .11. I was told this works great in northern
If you live in the desert south west you might consider windows with double (or more) layered low e glass on both panes. You would not notice the darker tint to the windows since the sun shines very intensely most days of the year. The purpose of this glass is to strongly block out long wave radiation heat from the sun. Unfortunately, the more the more long waves from the sun that you block out, the more visible light you will also block out, hence the darker glass. The extra low e does not lower the U factor significantly if at all. So that means it has little or no effect on the conductive heat inside your house exiting through the glass during winter. In technical terms, the lower the solar heat gain coefficient, (SHGC) the lower the visible light transmittance rating.(VT)
So, the answer to the question "Who has the best window?" would depend on what part of the world you live at.
For Wisconsin U Factor .30 or less, a SHGC (solar heat gain co - efficient) rating of .30 to .27, a VT (visible light transmission) rating no less than .50, (unless you don't mind dark glass) a non metal spacer system like super spacer or duralite. Metal spacers between the glass cause expansion and contraction during Wisconsin's seasonal changes which will eventually result in seal failure. Very important - make sure the window has a lifetime warranty on all parts, including glass breakage.