I wish I still had my PIAAs so I can do a side by side, but here's my take. PIAAs had the best color output, silverstars have the best light output. However neither hold a candle to HID

Here's a pic with OEM fog halogen(known for being some of the whitest halogen fogs around), and rebased osram d2r, known for being one of the more yellow hids. Now my camera doesn't like taking night pictures(the red over saturates), so they aren't that great but you can get the idea. Again top is 4300K hid with foglamps below on a white tarp, bottom pic is 4300k hid with silverstar highbeam on the same tarp.



PIAAs super plasmas have the closest to HID color, but not the best output, Silverstars are still pretty yellow(no where near as yellow as halogen) but they do have some pretty good output. I'll do this experiment again in a week or so with philips d2s bulbs in hella 90mm projectors for low beam, philips are a lot whiter and more blue than osram bulbs are, versus the silverstar 9005 high beams, then we'll see a clear difference.