Umm, PCBWING, the original poster mentioned immediately that they were using bus bars (smart I might add) for the actual conductor.
I'd use screw terminals for connection as already mentioned, if they weren't ment to be touched for a long period of time I'd solder them, in that kind of situation corrosion is your worst enemy, multi conductor wire will wick liquids and provide ample surface area for corrosion infiltration. I've seen 00 wire of ten feet or more become solid as a rock as it corrodes. Corrosion products increase surface area of nearly exponentially so if there's enough internal space to fit it, it will form a capillary system that will draw even ambient moisture up into the length of the cable, but because of the insulator it won't let it out, it's almost like a pump over time.
Over time this can even be a problem with laminated bus bar systems. To go extreme you either solder (if the temperature range allows) or weld the actual final electrical connections, or just do basic upkeep. Any joint exposed to air is instantly a fail point, if it's air permeable.