Metal halide is definitely better than black light. This is the reason why most late model branded platemakers use metal halide. The only platemakers I have seen using black flourescent lights are low cost locally made units.
During the early 80's, I used a platemaker with fluorescent UV black lamps. The main problems encountered were enlarged halftone dots and dots with soft edges.
Normally a 1,000 watts metal halide lamp is used for medium sized plates. Exposure would be about 40 seconds, depending on the distance between the lamp and the plate. Proper exposure time can be determined by using a device called
sensitivity guide. This can be purchased from Tritan for P450.
Metal halide lamps for platemakers are difficult to find. They come in 2 parts: the bulb and the ballast/igniter. I know an electrician who can assemble a 400 watt metal halide lamp. This lamp will give a good exposure in 2 minutes. He is Raffy Sandicho. His contact info is listed at
www.philprinting.com in the Opportunities section.
The best option, I think, is to buy a second hand branded unit from a dealer. You can get a good one (size: 22 x 30) for about P80,000.