I can only think of two possible issues with running sumpless:

- Cosmetic: Your heater, powerheads, skimmer, hotb fuge (if any)... will all be visible...
A tip to help reduce this... Put your heater behind the rock work or in a HOTB fuge.

- Less overall water volume. = less tank stability and more frequent water changes... But its only a 10g, so its not like you're changing out 50+ gals of water.

If you go this route, I have a couple cool DIY things to help keep it looking good.