If there is any difference, you wont' notice it. I believe it takes something moving around 1700fps to start the chemical reaction that creates the big boom - whether you are just above that or significantly above that won't make a difference, to any appreciable degree anyway, because the chemical reaction is going to happen at the same velocity (60k fps?).
I've still got a 1 pounder sitting in the garage waiting for an opportune time to detonate. 1/2 pounders are lots of fun - but be warned. They WILL throw debris much further than you think, and you will spend a lot more time picking up the aftermath than you anticipated, which generally turns into a ticked off wife when you get home an hour late and then spend another hour watching the video over and over again with your buddy while laughing like a 5 year old.
I put a 1/2 pounder inside an old aluminum turkey pot that had a bunch of leaks. Pure awesomeness - and the pot had to go a good 50 feet in the air. Destruction was complete.
I've heard of people prarie dog hunting with it, but I've not experienced it personally.