The following response may not be in the best order but I did my best to address you and make it look as good for you as possible.
I don't get how you can sit there talking about Band/Specs on other Pokemon being comparably as effective as Latias. You are seriously underestimating the whole package that Latias provides, which no other Band/Specs Pokemon can boast: bulk, power, and speed. The point is, Latias easily finds ways in because of its excellent defensive typing and ability, outspeeds 90% of non-scarfed OU Pokemon, and slams things with its insane Special Attack. The speed is the differentiating factor here when you consider a Pokemon's ability to sweep. Sure, CB Tyranitar and Scizor, or Specs Heatran can hit things hard, but then they are easily outpaced for a revenge kill (key word: "easily" because most Pokemon need Scarf to revenge kill Latias). On top of that, it's harder for them to come in and spam an attack, as even though they are bulky like Latias, they are often outpaced by Pokemon in OU, meaning they only have the option of switching in on things that cannot KO them, whereas Latias can switch in on things that CAN KO her, and still force them out because she can simply KO first. To top it all off, Latias can pretty easily just spam powerful attacks while remaining unscathed (due to her speed) unless placed in an extremely specialized metagame, where so many Pokemon are dedicated to ensuring this doesn't happen (see: Scarf Tyranitar). You are very naive if you think that Latias is even comparable to any other Specs user in OU. I'm not even going to go into detail about the near un-resisted STAB that Latias has, which no other Choice user can claim (bar Salamence, but I think Salamence should be tested for Ubers anyways).
First thought that comes to my mind when comparing Choiced Pokemon is that they are not sweepers, but rather they are employed on a team to break down the opponents team to set up a sweep for another Pokemon or to put yourself at an advantage over the opponent. From there I think about power and how important it is; the stronger the Pokemon, the better it will be at doing this job as a choice user. Then I think about how many times it can go in and out. And that's how I think about Choiced Pokemon.
Now then, you bring up the package that I was curious about when Ashley replied to me. Bulk, power, and speed, huh? Well first, I'd like to critique this package. I don't see speed as important. It might be important if you plan on sweeping with something, but not if you're using a Pokemon to blow holes into the opponent's team. The important thing there is power first, bulk and the ability to switch in second. Speed is not important on these Pokemon, as they are not meant to sweep. It's just a bonus. So for a Pokemon to do it's job efficiently as a Choice User it needs to be able to hit hard and find time to switch in; it does not need to be fast to do it's job.
Now then, in this metagame (Standard, not suspect) there are plenty of speed boosting Pokemon and plenty of priority user and plenty of scarf users. One quick glance at the top ten and nine of them use of these things commonly. This is another reason why speed doesn't matter. Latias isn't going to have the time to sweep like you would like it to. It's going to hit / kill things and either die or come back and hit / kill things. Myself and other users have already said this in the thread. When was the last time you killed something with Latias or something switched in and Latias wasn't threatened and forced to retreat? It probably happened more often than not. That's because it doesn't matter how fast Latias is, it is stuck on a move that is going to allow something to threaten it or even kill it .
As for bulk and power, Heatran has 91/106/106 Defenses with 12 resistances and immunities; Latias has 80/90/130 and 7 resistances and immunities. I'd say the bulk and ability to switch in are pretty comparable. As for power, I've already shown it's power. Without a Heatran, Blissey, or Snorlax, this thing is going to do probably more damage than Latias would. It definitely is comparable with Latias as a Specs User.
Anyway, you seem to be hung up on Specs Latias being a sweeper. Well, it's not. I mean, sure, it can be if you eliminate the Pursuit user on your opponent's team, the scarfers, priority users, and you make sure it's safe to use Dragon Pulse or something, but I could say the same for any Pokemon. Make it easy for it to attack and have no threats to it, sure it can sweep. Specs Latias is a wall breaking-esque Pokemon. It blows holes in the other team, like other Choice Users.
From here you say that these other Choice Pokemon have the ability to switch in only on Pokemon that can't KO them while Latias can switch in on Pokemon that can KO it. Well, I personally would not switch my Latias in on Scizor, Tyranitar, Salamence, Latias, Jirachi, Metagross, Gengar, Lucario, Starmie, Breloom, Gyarados, or Machamp. I guess you're talking about something like Rotom-A or Swampert? So I guess Latias can switch into Defensive Pokemon, but so can other Choice Users?
And finally, about Latias spamming attacks and remaining unscathed. I kind of already touched up on this but I guess I'll expand. Unless the opponents team is odd, they probably have some way of threatening your Latias after making a kill. This could be Pursuit (Scizor and Ttar being the top two most used Pokemon) or a Scarf Pokemon (Jirachi, Latias, Heatran, Rotom-A) or priority (Scizor, Lucario). You could also be set up on if you use Draco Meteor or Dragon Pulse or forced out (say by...Metagross, Jirachi, or Empoleon).
Personally Phil, and no disrespect here, you appear to be naive. You seem to think that because Latias is fast it suddenly is more powerful than other Choice Pokemon. But it's not. Why does speed matter? So you can outspeed whatever you're switching in on? You wouldn't switch in on something unless you could threaten it anyway, whether you outspeed it or not. It's power that matters as a Specs User, something that other users can match Latias at.
I wish to reiterate the following point - Specs Latias is not a sweeper. If you use it as one, you must support it like you would any other sweeper. Specs Latias cannot sweep if there are Steels, Pursuit users, strong priority or Scarfers on the opponents team. It will be forced out or beaten every time. These things are prevalent in Standard, and aren't just in a specialized metagame. If you sweep with Specs Latias without giving it any support, I'd love to hear about how you did it, because I don't see it happening. I see Specs Latias doing what every other powerful Choice User does in OU - do large amounts of damage to the opponents team and make it easier for another Pokemon to sweep.