You're forgetting at least two other designs, the HouseWrecker and... um... (points to sig)
I believe there's also a dual Alpine type R horn around here somewhere that should be plenty mean itself, SPL wise.
There are advantages and disadvantages to all of them. I won't speak for any design but my own. Within Xmax, 350W into the box, it will do 116dB at 20Hz, 1M, in half space. Let it pass Xmax and explore the drivers' mechanical limits at 600W in, it'll do a little over 118dB. It's designed to get the most out of a single EP4000... one of those amps can power four of these boxes to the 117dB @1M half space level each. I can't even imagine what that would do to most rooms with quarter or eighth space loading. One can be done around the $500 mark.
Disadvantages? I compromised the horn flare to get it to fit in three sheets of stock before bracing, therefore it loses some sensitivity in the middle of the passband. Uses 10" drivers... you can only get so much from a pair of drivers that size, and I believe I didn't leave a lot on the table. And it's big... no getting around that with a 16Hz horn of any kind. That said, I made it as flat as I could to make up for the size in the other two dimensions.
Anyway, that's what I bring to the table, until I win the lottery and I can start moving forward with some of the more potent stuff I've been playing with in Hornresp.