Fluorescent, simply because it is a lot more efficient and won't contribute too much heat to your tank. Both will encourage algae growth, but you'll need a lot more power with incandescents.
I personally like to use 36w 6500k compact flourescents over my 10g tanks that contain macroalgae, and that works great. You can usually get a ballast on Ebay that will run 2 36w cf bulbs for around $13. I think the bulbs run about the same price. You can get 1/2" conduit hangers from the hardware store, and with a little bending with some pliers, they make excellent bulb clips. That might be more info than you wanted, but I hope that helps.
Hi Nautilis, if you haven't already, check out www.ahsupply.com for their DIY kits, cheap and well made. I've ordered several and liked them. A 2x13watt kits would be great for a 10 gallon. brandonberry's suggestions are also good.
