Other then more power handling and slightly less loss. I see no reason for using 450 ohm window line. Or are you asking about 450 ohm twinlead and not windows line?? There is Twinlead, Window line and ladderline. It seems like a lot of hams get these mixed up. while they are all balanced line there are subtle differences
I don't like the common 450 ohm window line as I have found it very unstable in wind and rain. Interestingly enough the 300 ohm twinlead seems more stable?? The 450 ohm window line seems to be an eyesore, it really stands out. The stuff is visible blocks away.
For low power, I use the 300 ohm stuff form Rat shack. For higher power applications I completely bypass the 450 ohm window line and I build true 600 ohm ladderline. Even though the home brew stuff is bigger it doesn't stand out as much. I paint the insulators with different colors of military camouflage paint so the insulators disappear into the background.. It's amazing how well that camouflage paint works. It works so well I've had people walk right into the ladder line as I was building it.
As far as impedance is concerned, its not that critical. The loss is so low that even with a high SWR the difference between 300, 450 or 650 ohm balanced line is negligible (Assuming low power =>100 watts). The only real difference is stability and power handling. What's really interesting is that on paper the 450 ohm window line should be more stable then the 300 ohm twinlead. But in my experience the 300 ohm twinlead is more stable not only that but its easier to bring into the shack.
[QUOTE]The box said 'You need Windows XP or better' .... so I installed Linux[/QUOTE].