I've previously used an Osram Night Breaker Laser in mine but, last year on recommendation from our UK Truffle Sniffer, I switched to an
AUXITO H4 9003 LED Motorcycle Headlight Bulb (£12.50 delivered from EBay).
It's no bigger than the incandescent in the headlamp shell, important as space is at a premium, in there.
Only been in for a couple of thousand miles, so far, without any problems.
It's less expensive and significantly brighter.
No issue with dip cut off, it sailed through an MOT Test.
According to the specs., it uses only 28 Watts.
The only noticeable wrinkle is that it pulses, in time, when the indicators are used. I'm not sure whether that's a plus or a minus, but it doesn't bother me.
I'll report if, and when, it fails unless it reaches it's claimed 30,000+ hours, in which case, I might not be around.

