I'm partial to Hellas, and don't have any experience with other manufacturer's wiring harnesses. I usually just buy the lamps, and not the harnesses, but sometimes the lamps are supplied as "kits" and include switches, relays, and wiring. Hella's instructions are simple to follow.
My preference is for Hella 4000 lamps on the front and 550 lamps on the roof. I prefer the 4000 lamps with the "city Light" feature, as 10 watt bulb inside the lamp housing, that is enough to attract attention from other drivers, not intended to provide the driver with lighting. Many European cities do not permit the use of main beams while inside the city to keep down excessive light polution and glare.
There are many suppliers that sell direct for way less than the advertised prices in the AB and RN catalogs.
These people have great prices and next day delivery. http://www.rallylights.com/