It is entirely possible that at any level given most basic team builds that certain strategies are hands down better than others... It really depends on the GE design etc. etc.
We can not assume that the tactics are balanced. Too much has gone on to even suggest they are balanced. Can you get away with zones? YES!! Is there much evidence they actually work as well as MtM? No... I am somewhat of a believer that 2-3 can work against inside attacks. I find it hard to imagine situaitons though where it was better than MtM...
THe situations I think 2-3 might be better is if the opponent has poor flow and a no outside shooting to speak of. In this case you can force them into outside shots they will miss and control the glass. At higher levels teams tend to have a few shooters and/or really good flow, so the zones are much less successful.
In terms of pure defense, I'd agree that it would be rarely, if ever, better than or even not worse than M2M, certainly given the composition of most rosters right now (and I personally don't have experience with the high ID/OD/SB combo to objectively evaluate that). Just last week in a fed we had a discussion about one of our fed member's upcoming Cup games against a league rival and because of the very situation you describe (poor outside shooting, unimpressive flow) and because the opponent usually had a massive rebounding advantage, the fed member went with the 2-3 and pulled out the win. The opponent, incidentally, also ran a 2-3; which meant in a cup game in a big country featured two teams independently playing LI/2-3 against each other in a neutral site round, something which really surprises me.
Oh, before I forget, the thing about different tools for different jobs and all that isn't at all predicated on tactics being balanced. I do think that it is somewhat level dependent though - one of the main reasons why "outside offenses don't work" is that it's just financially crippling to try to build a team with enough offensive skills to shoot outside over top level teams' OD monsters, especially with the way that JR jacks up salaries when it gets pretty high. But for probably at least 35000 users, the levels of OD that they face in their league doesn't rise to the level where they're financially crippled. I do think it's a shame that the way the salary formula works and team composition at higher levels means that if you do end up competing at the top level, you're constrained into either doing the same thing as everyone else or being a guinea pig for an unproven strategy.
I wish the zones were not like offence, in that when you add one thing in one place you give up more in another. THe boost to rebounding and inside D of 2-3 is set so that you give up a lot of pressure. I think the give-take should be more balanced. This would make the defences more adaptive and force offences to be more creative/varied. Just more fun. If the 2-3 zones gave up only outside shots, but didn't reduce pressure on passes (for example) this would make it much more effective to stop LI, but it would still make the team vulnerably to Motions and R&G etc.
I'm not sure if you know the answer either, but I keep meaning to try to ask. We know that OD stops passing, but is there any sort of information on where, specifically? For example, the OD on your guard matching up on the guy making the pass almost certainly helps affect the possibility of the pass going through, but is there also a check on the receiver, where the big man's OD may be checked to see if he helps prevent a pass into the player he's marking? And then would that be based vs. his man's driving, for example, or the guard's passing, or the team's flow?