I spent quite a lot of time assessing LED light units instead of bulbs on my mini, my thoughts:
They are no brighter than high intensity halogen such as Philips extreme Vision/Osram nightbreaker. I fitted one of the leading brands 12 with a high tested output (12 months ago). Took light meter readings and took photographs in manual mode to compare detailed information in the distance.
If you spend enough money you can get equivalent beam patterns but if you buy cheap the beam pattern is likely to be different as the point source of the light won't match.
I am suspicious about the life expectancy (although i have no data to back this up) LEDs for high intensity lighting run VERY hot and the claimed life is seldom met, so they could end up being very expensive.
They make the car look nice, but that is subjective.
The crunch for me was they are not road legal and risk invalidating your insurance.
Regarding DRL I would also like to find a good solution that is road legal. It is a bit of a grey area with DRL lights but I would like them to be e-marked. There are some around, Philips and Osram make them, but the styles don't look right for the Z4.