I tested lots of lights too.
our 5s-fe has now Philips XP that are very decent (better than Silverstars for sure), but honestly there is no good H4 bulb which will make the low beam strong enough for me unless I go HID ... and I did, tried a 4300K HID kit behind a clear reflector lens (no projectors though) for 9 months, but hated the glare and lack of clean cut off, light color phasing over time (from white they went towards pinkish). having no money for real retrofit and generally being pissed with xenons I sold them and we went with Philips XP being the advertized (marketing) winner.
Sylvania XtremeVision bulbs sound like a good option too
me neither sees any significant difference between most H4 halogens, the light output is pretty much always similar if not same (crappy) for most.
I'm not talking about tinted bulbs where whiter/bluer lights seem stronger
because eyes get blinded more thanks to change of spectrum (it's a mind trick).
those colorized bulbs suck big times, they as said many times trick eyes into believing that whiter/bluer light means brighter (that's how human eyes react to those colors), but in fact lumens (true light output) amount is LOWER with those blueish lights and every automated meter will prove that.
However the only REAL difference I see is on my V6 where I used older Toshiba HIR2 (9012 trimmed to fit 9006) as low beams and man I love those
I also have clear fog lenses on that car, so over time I will also install HIRs in fogs too, for brights I will I think go HIR again (9011 trimmed as 9005). that would be a sweet setup
HIR is a perfect option for regular 9005/9006 lamps, no ballast crap to mount as with HID, no extra crappy wiring, no rusty ground problems and flickering lights, no long bulb warmup (try flashing HID brights from off to on, it looks ridiculous like something was exploding), simple plug and play.
... and they give around 75% light output of a HID while keeping the price real low, only slightly higher than decent halogens. I wish they made a HIR H4 compatible bulb finally, but I guess the dual filament in this application is a tough technical problem? or maybe H4 is not a common lamp base anymore and was abandoned?
I have Phillips HIR2 in the low beams and Nokya Artic White in the fogs and they light up the road, better than new cars. Like Bdub said, the Nokyas are pure white.
I've played and played, and payed and payed, for so many light bulbs that I can't remember all the brands and names. If you have a good reflector or projector system in the first place (like Bedub215's Lexus), maybe it can make a decent difference, but most of the time It'll just look a little cooler (from the outside). Most of the time. all the claims of 30% brighter, and 40% wider, have been invisible to my eyes.
For certain, all the claims on higher color temp. lights being brighter are bogus. (blue tinting on the bulbs, reduces the visible light and lumens sent out)
The only thing that will make a really noticable and useful difference to nightime illumination is a projector retrofit, in a suitable set of clear lense headlight units. Preferably with HID bulbs. It's like having 5 sets of Gen3 or 4 headlights working all at once and putting the light where it should be.
-Funny thing is, I once had a set of Bosch halogens on my old 76' Celica GT, (a round, 4 light system), that had nearly as sharp of a cut-off, and put out nearly as much light with 80W lows, and 100W high beams.