My signature probably gives away which sirens are my favorite, but specifically I love the Sentry 40v2t. Just watch this video of one running one mile away from the camera and you'll see why. It can run on batteries too. Definitely the best siren being made today.
I also love the 3v8 or the 3v8-H sirens. They are very low in power, like the Model 2, but are significantly louder. Perfect for small areas or fire departments in smaller towns. The deep tone still carries pretty far for the amount of power these sirens use. They definitely beat the Model 2.
In terms of electronic sirens, I do like Whelen over Federal Signal and ASC, specifically for the air horn and hi-lo signals. They also carry REALLY far. Even the small hornet can be heard for several miles if the conditions are right. The only downside is they have poor structure penetration, but these are meant to be heard outdoors, right?