Paleo - One hole or several holes through the bottom of the pot doesn't impact the maximum ht of the perched water table, and it doesn't impact how well the soil drains. It will just cause the soil to drain a little faster, but plants don't care if it takes one minute or 10 minutes for the pot to drain. If the holes are in the side walls, it will probably increase evaporative water loss - a good thing if your medium allows you to water properly (so you flush the soil as you water), but not a plus if you're forced to water in small sips,because that practice ensures all dissolved solids (salts) from tapwater and fertilizer solutions remain in the soil where eventually they limit water/ nutrient uptake and skew the ratio of nutrients in the soil.
Lucy - I'm not sure about the rules here, but I can link you to a thread on another site, or post a thread here on the container forum that addresses ways to limit water retention in container media, even for media inherently too water-retentive to offer plants the best opportunity to realize their genetic potential. You'd love reading about how you can use Newton's First Law of Motion to rid your manageable size pots of ALL excess water.
Al
