Most studies put Vinyl windows as 70% more energy efficient than aluminum...
Levels of vinyl efficiency...all vinyl is not created equal
1. Cheap vinyl with regrinds (recycled vinyl) dual pane - air filled
2. medium grade vinyl - dual pane - air filled
3. pharmacuetical / virgin vinyl - dual pane - air filled
3 levels of vinyl - dual pane - Low E (silver / titanium / zinc coating on glass working as mirror to reflect UV)
3 levels of vinyl - dual pane - Low E - Argon (gas between panes of glass to stop convection heat transfer)
3 levels of vinyl - dual pane - Low E - Krypton (double R value of Argon)
3 levels of vinyl - 1" dual pane - Low E - Argon / krypton (wider dual pane more gas)
3 levels of vinyl - dual pane - Low E - Argon - Intercept Spacer / SuperSpacer - (type of spacer that holds gas in)(***very important***)(bad spacer = thermal efficient gas goes bye-bye)
3 levels of vinyl - dual pane - 2 sides of glass Low E - Argon (low E coated on both inside glass sides)
3 levels of vinyl - dual pane - 2 sides of glass Low E - Krypton (Simonton Solar System)
If you have the money, the best vinyl window combination (non-hurricane) - Multi chambered fusion welded high grade vinyl frames/sash - 1" dual pane w/PPG architectural grade glass (thicker) - 2 coats Low E - Krypton gas - SuperSpacer - PPG Sunclean self cleaning glass