I use and LOVE the Showmaster black glass gravel! The good points: Easy to clean, Doesn't alter PH, Small smooth pebbles (fin friendly), Looks awesome!
The bad points: It's very expensive I use it in my display tanks so it shows up the fish and plants beautifully.
As we all know when you use a substrate it will 'collect' all the nasties so it does need a thorough cleaning to remove them. I only use a thin layer about a 1/2 inch to aid the cleaning process and I have found this gravel to be the easiest to clean, I have other substrates including sand (extremely high maintenance)in my tanks but I'm fanatical about WC's and tank cleaning....
Good luck with your choice I hope this was helpful :)