AJ, there are a variety of laser marking systems in the marketplace. Most use a CO2 laser to mark PCBs. Since laser life is directly related to power available vs power used, you should try to get a system with a 30 watt power rating. Most marking is conducted in the 12 watt range.
Next look at user interface. How easy is the system to program, what types of markings can it perform (you never know what you need to mark until you need to), accurancy, and in line capability.
Most marking systems should perform: 1D, 2 D bar code martix, code 39, date and time, lot, numeric sequencing, lot sequencing, text and graphics.