I was leaning to the tubes but after looking a little closer the hoods seem they would direct more light down. Also if the tube breaks, your screwed but if the glass breaks on a hood you go to the hardware store and have them cut you a piece to fit. Has anyone ever seen or owned both?
I owned both and went back to a Cool tube. They are lighter. The vented hoods take up almost 10" more space where it counts vs a Cool tube. If height is critical, a vented hood may not be the way to go.
I was in the same situation, i went with the cool tube, and it is awesome for me. and i have enough height to use a hood if i wanted to. If you buy a quality tube your glass should not break as long as you have air blowing through when your light is on at all times.
or if you don't mind a bit of a DIY get a pyrex bake a round glass tube on ebay, as well as a mogul socket and a couple fittings. The cool tubes usually run for around 100, but the DIY is in the 50 range after all is said and done. (a bit more if you over pay) I'm running a 600w HPS in a 3.5" pyrex tube. The room is about 6-7 degrees cooler with it, so it's definetly working. Most people don't go over 400w in a 3.5" tube but it works like a charm for me.
I have both and prefer the hood, it is a few inches taller but runs cooler and has a more even light output. It's damn heavy compared to the tubes though!