Maybe he's not looking for a bong this purchase. What if he has 20 glass bongs at home and now wants a gravity bong? That's not the case, but still. He wants to know which of the two are best, not whether or not he should get one.

However, when it comes to gravity bongs, I like the ol' 2-liter and pitcher technique myself. It's almost free (if you have a 2-liter around the house it is) and it's pretty simple to construct. There's plenty of tut's on how to do it on the site. If you don't have a pitcher or a bucket around, go for the kitchen sink to hold your water.

Also, the bukket is pretty nifty.