This thread started, if I recall, with a poke at people that dive big tanks. A completely undeserved, uninformed poke, in my opinion, but that doesn't mean that more is always better or that bigger is always better, even if we're talking about air in a scuba tank. Saying that something isn't necessary isn't the same thing as saying "it's bad".
As Skittl has mentioned and as others have, there are reasons that people don't want to dive big tanks. Ron, more accurately, you *need* to make it a multilevel dive in order for the 120's to get more bottom time than the 80s. As you know, 60 feet for 60 minutes and everyone is done, no matter how big the tank on their back.
Case in point, I've been diving with Scubamex in Paamul on two occasions. I think I've done 9 tanks with them. Well, that's the profile. 60 feet, 60 minutes. The people diving over there dive 80s, and come up with gobs of air. One morning, there were 14 divers on the boat. 3 of us weren't dive instructors and just about every agency was represented. NAUI, PADI, SSI, YMCA, etc. If you told them steel 120s were better because they have more air, they'd laugh at you. Hard.
So would Ralph. Ralph started diving long before there were any agencies. I did a Blackbeard's Cruise many years ago, and Ralph, myself and a gal from England were all loners. The three of us were buddied up. Ralph did the first two dives with us. He was obviously very advanced. Third dive, he told the gal and I that he was only going to be doing short dives so when he leaves, don't worry about him. For the rest of the week, Ralph did 15 to 20 minute dives and probably got back on the boat with 2000lbs left in his tank. Or more. You could strap double 120's on him, but for what? The gal (Karen I think?) and I talked about Ralph and we both figured the only reason he did the first two dives with us was to make sure we were OK on our own. Sweet guy.
Big tank diving isn't better diving, and it certainly isn't worse diving. It's different diving, and though it took awhile to get there Mike, your last post is a great advertisement for big tank diving and I'd like to hear more besides just the one Throat example you used. (Like, how do you dive other sites, specifically. Cedral? Palancar?, etc.) I'd like to try it and as mentioned, I almost got to last trip. There are considerations, though. For me, neoprene, weighting, NDL, hydration, etc. Besides "seeing what's over the next hill", I'd also be interested to see what kind of a dive day that makes. Right now, I leave in the morning and come back at supper time, all day, almost every day. I love it. To be fair though, on the day/s we did two tanks only, having the afternoon "off" really made the trip stretch. I suspect that doing 2 really long tanks get's you back a little later in the afternoon? 2ish? 3ish?
As for me, and I suspect for others here, AL80s fit the bill, and if it isn't broke, don't fix it. That doesn't stop me from wanting to experience diving a/some big tanks, but there are considerations, for sure. The fact that there are operators on the island that use big tanks is another one of the things that makes Cozumel such a great place to dive.
-Blair