Colour temperature
Car bulbs can produce varying light colours, measured in Kelvins (K). Most standard halogen headlight bulbs have a yellowish tint, which is around 3200K. As you get further up the Kelvin scale, the light gets whiter. Road legal halogen bulbs can reach heights of around 4200K, which will produce a whiter light in comparison to a standard bulb colour.
Both the Philips DiamondVision and the PIAA Hyper Arros 5000K fall into the Styling category of bulbs. This means that they produce a stylish, modern look on the road. If you're looking for a halogen bulb that's a close colour match to a xenon HID, choose one of these ranges.
The Philips DiamondVision produces a colour temperature of 5000K, which delivers a strong, white light with a very slight blue tint. Similarly, the PIAA Hyper Arros 5000K produces a cool white light, with a Kelvin rating of up to 5000K.
Both of these ranges are an ideal choice for those seeking a cool white light. If you're after light colour only, the DiamondVision has the slight edge here - 5000K in comparison to the Hyper Arros' up to 5000K.
Brightness
In many cases, styling bulbs use all their power to produce the whitest/bluest light possible. This means that the brightness and beam length will be comparable to a standard bulb. You'll see this in the DiamondVision range - its purpose is to enhance the styling of your vehicle, not to produce any extra light on the road.
This is where the PIAA Hyper Arros 5000K comes into its own. The range utlises Japanese and Korean manufacturing, plus a perfectly positioned beam placement, to make the light 120% brighter than standard. With the Hyper Arros 5000K, you'll get a good mix of style and performance.
Road legal
It's a tie for this round. Both ranges are not road legal, due to their colour temperature. Halogen bulbs are usually road legal up to 4200K. Any higher than this, and most laws state that the light colour of the halogen bulb will be too white/blue and could be mistaken for lights on emergency service vehicles. As both ranges come in at around the 5000K mark, neither are suitable for on-road use.
So, which bulb is best?
It all depends on what you're looking for in a bulb. If you want the most stylish light possible, and don't mind the light output of a standard bulb, choose Philips DiamondVision. Those seeking more of a blend between style and performance should go for PIAA Hyper Arros 5000K.