Its simple. Unlike sleet storm, you dont need to be on top of enemies to do dmg with archon destruction wave, it also goes thru obstacles like walls so you can pretty much hit anything on the screen, these benefits dont show up on a ghom test.
Sleet Storm has Teleport in the build. Archon won't if you have Improved Archon. And you'll need Improved Archon to match the dps output of Sleet Storm.
Sleet Storm applies Cold Blooded 100% of the time to everything you hit with it. Archon has to rely on Scoundrel with a Buriza with very high pierce, who may or may not be hitting everything you're hitting. And he dies sometimes which is largely outside of your control.
Both the best Sleet Storm builds and the best Archon builds will have the following abilities: Glass Cannon, Magic Weapon, Cold Blooded, Critical Mass. Archon will have Sparkflint, whereas Sleet Storm will have Deep Freeze. Archon typically runs with Pinpoint Barrier, and Sleet Storm can as well, or they can use Shocking Aspect which actually procs quite a bit with channeled spells (see Apo's sticky and the tests that they've been doing with regard to CM and SA procs).
Archon has a much higher EHP potential, and a sheet dps advantage over Sleet Storm. But a 1H Sleet Storm build will be using Chain Reaction, which does about 100% more weapon damage than Improved Archon's Arcane Blast. You have to be in melee range with both builds in order to take advantage of these, so if Archon wants to use it, it negates the ranged advantage everyone likes to boast about. That means that if Archon stays at range and Sleet Storm Teleports right into a pack, Sleet Storm will be doing an extra 291% weapon damage per cooldown period (which is basically 1 second or less against trash packs and clustered elites). So the sheet dps disadvantage of Sleet Storm is more than made up for by Chain Reaction in a lot of situations. Some of the higher EHP potential of Archon is made up for with Safe Passage and Frost Nova for Sleet Storm. Both take attack turns, so that can cut into dps times a little bit for Sleet Storm.
1H Sleet Storm with 3 sources of APoC can sustain perfectly fine, even against singles and even while spamming Chain Reaction on cooldown, and even when adding IAS everywhere it can.
If you want to compare potential with gear, you have to compare the very best Mempo for Archon versus the very best rare Wizard hat for Sleet Storm. Rare Wizard hat can potentially be 300 int, 6cc, and 7 extra RoF CC. Compare that to 9 ias, 6 cc, and 200 int on Mempo, and Sleet Storm's best helm - from a dps perspective - is better than that of Archon's best. However, 6cc Mempo's are easily available (if you have the gold) whereas a rare Wizard hat like this for Sleet Storm probably doesn't even exist yet.
The very best amulet for Archon versus the very best Mara's with an extra int roll, CHD, CC, and bonus RoF CC is another comparison to make. From a dps perspective, a trifecta Tals would be the best for Archon I would think. That would be a slight dps advantage over the Mara's for Sleet Storm.
If you go with 3 APoC sources for SS, they'll lose a lot of extra CHD if you go with LS on the wand, so Archon has the advantage there. Archon also gets more int on source since SS will have to go with an APoC roll on their Triumvirate.
Other than that, both builds can use the same exact gear in the other slots.
And the biggest thing everyone forgets about is that when you're surrounded by mobs, Sleet Storm is hitting everything around you, whereas Archon beam is only hitting the stuff in front of you. That means that after Archon is done killing the stuff in front of them, they then have to swing their beam around to kill the stuff behind them and to the sides. Sleet Storm doesn't have to do this since everything around them is dying at the same general pace. This advantage that SS has over Archon might not be as apparent during trash sometimes, but it is against melee-type elites that come at in you groups of 3 or 4 and completely surround you. In those situations, Sleet Storm is killing all of them at about the same time, whereas Archon is only killing 1 or 2 at a time, then has to swing over to kill the other 1 or 2 that are left, effectively almost doubling their kill time. Archon has an advantage over SS when it comes to ranged mobs, but with skillful use of stutter-stepping, Teleport, and Frost Nova, the advantage isn't as big as everyone makes it out to be.
Sleet Storm can easily Teleport out of things like Frozen and recover easily from knockback and fear with Teleport as well. Archon can run out of Frozen and then continue to dps from where they end up, and can also continue to dps from where they end up after a fear or knockback. The difference in the dps loss between the two is probably negligible since the cast time of Teleport is static at .333 seconds no matter how high or low your APS is.
So it's not as cut-and-dry as a lot of people believe between the two specs. Both have their advantages and disadvantages over each other. Archon is generally much, much easier to play and gear for, but a skilled Sleet Storm user will know how to work their strengths and deal with the disadvantages in order to make up for lost ground and put them on more equal footing. I'd put my Sleet Storm against an equally geared Archon any day. Not saying I'd necessarily win (unless it was VoA, where I'd trounce all over them due to Teleport shortcuts and never having to worry about refreshing Archon cooldown on trash), but I'd give them a DAMN good run for their money. Anyone up for the challenge? :)