The Zoomed 5.0 or 10.0 is better.
In tests the UVB output is higher/ further reaching and they are supposed to last longer.
I have had good luck with them .... have not tried the exoterra.
Regardless they need replacing every 6 months.
I'm going to list these links in an odd order to show you the numbers and then the explanation links :
The index # is a ratio between one part of the UVB spectrum and another part of the UVB spectrum. The numbers are normalized to the sun's actual ratio and set to 1000. Overall uW/cm2 is only one part of the chameleon equation . I think what you are looking for is a number that approaches the 100 number of the sun. Having a lower number means that the ration between to two important portions of the UVB spectrum are not in the most beneficial proportion. (I haven't re-read the article since it came out .)
If the D3 Index Table is to be understood to represent "goodness" for our chameleons then the Zoomed Reptisun 5.0 wins. The 10.0 wasn't tested during that research because it wasn't available at the time. The "UVB Guide UK" site is loaded excellent data and more testing is in progress. The Reptisun 10.0 isn't as well understood for chameleon applications because it doesn't have as much actual chameleon keeper history yet (Catch-22 ). It's visual light output is dimmer than the 5.0 while its UVB is higher. Higher UVB isn't always the goal otherwise we'd all be using high UVB output mercury vapor lamps (Mega-Ray is one of the best, if not the best.) like iguanas keepers use and for zoo applications etc. We tend to stick with the Reptisun 5.0 because of its proven track record. With chameleons, its an effective way to eliminate one more variable of husbandry that may influence your chameleon's health. As Brad mentioned, with the Reptisun 10.0, its higher output will "reach" farther into an enclosure but that also means if your critter is only 6" away from the tube then it will be getting a potentially higher level than may be best .
If you only had a choice between the Reptisun 10.0 and another mfgr's tube, get the Reptisun 10.0, otherwise you might stick with the Reptisun 5.0 tube... Tricky choices...
P.S. I'm not a big fan of the coiled tubes. Energy density is even more concentrated into a smaller area and the ballasts have a high(er) failure rate; some have (rarely) even exploded .