Double glazing/new windows for house

[mszebra]

Our soft-wood double glazing windows are rotting, SO we are thinking to get PVC replacements.
We are thinking about Planitherm glass because it has 1/3 less heat loss than the industry standard Pilkington K.

Just wondered if anyone else has any tips, thoughts, experiences about how to choose which company to do our windows?

we were going to get planitherm but the salesman (who sells both types) says apparently it does not allow as much light through as normal pilkington K. He suggested the best combination was Pilkington K with argon as a filler between the panes - has nearly as low as a value as planitherm.

Have never actually had double glazing so no actual experience !

You know we were only thinking Planitherm because YOUR DH suggested it, Throck.
2/3 of the guys who have quoted us had never heard of planitherm. But the one who did, said something about Argon....

NOw I've looked into it... it's the industry standard Pilkington K that has haze problems; the planitherm (alternatives=Pilkington Optitherm, or Interplane Iplus) don't have the haze problem!

Am still intersetd how people figured out which windows company to go with. Personal recommendation? Price? Salesman charm?