General concensus is - the lighter the better.
That being said, close to every string-set on the market has got bad gauge-balance when it comes to slapping, and much more importantly popping. I'm currently using a composed set of 45-60-80-105-135, switching down to 40-55-70-95-130 - tuning down a step. Though just switching down the gauges on the D and A-strings on the first set (or C and G as it'd turn out with my tuning) makes slapping and popping sound MUCH better, due to the lighter mass, not to mention that the output and feeling is much more balanced due to the balanced tension as well.
So, final recommendations on string-gauges: if you like your stuff REALLY light, go 35-50-65-90, or if you want more tension to it, try 40-55-70-95. Try a .100 on the bottom if you want more tension there. Alternatively, go 45-60-80-105 if you desperately need tension. Any larger on the low-end will not lend itself well to slapping (talking about four-strings). If you've got a five-string, basically anything between .120-.130 works. If you're looking for balance, stick between .125 and .130. I've got a .135 on my bass right now - not that much of a difference in tension, but there's a trade-off when it comes to slaptone, hence my going back to .130.