They are chip magnets, and simply take up chip/card real estate. Secondly, cupholders in the play surface are to be avoided if at all possible. In other words, you try to go onto Craigslist and you'll find a ton of hex tables for next to nothing (can't give them away), and fewer ovals (which I think are more desirable). An oval allows more room, and is more standard (current) on the poker table front. You can barely fit 8 people at a hex table comfortably, and certainly not 10.
OK, for starters, I think a oval is the way to go.
