Epic 3 watt (3000mW) Blue Laser 101 Balloon Pop 

Lunaphase Lasers yes, but blue seems to be the best price per watt right now, still fun as hell to see them do things like this :) of course you get what you pay for and maybe a green one would be better but at almost twice the cost haha

Best price per watt overall would probably be Co2 lasers. But they don't produce visible light (Far infrared, 10600nm) and are therefore boring I guess? You can pick up a 40W tube for about 100 bucks. As far as handhelds go, green would probably be the best for poppin balloons, yes. DPSS tends to have the tightest beam diameter and lowest divergence for the form factor, so a 532nm green would be the one to go with.