Both of them are very effective against one opponent, but against two they really fall apart.
The things I've specifically noticed are that they both suffer from an action defecit. Against one opponent, that's not a huge problem because your single opponent is often in a similar situation, and if your figures can stand a little pushing while dealing significant damage, you still have the upper hand.
But against two opponents that tactic doesn't work to your advantage. When you push, you invite reprisals from both opponents. It's like pushing and then not being able to act for two turns against a single opponent.
Also, both of the teams I played had sacrifice/tie up pieces built in. But in one game, by splitting my forces, I wasn't able to use the sacrifice figs in their intended roles, (they got tied up with the wrong opponent, away from the main attack figs). In the other game, I was able to use my sacrifice figs appropriately but I split my main attack groups and just wasn't able to bring enough firepower to bear on either opponent to gain any advantages.
I think it really is a different build style for a 3 way match compared to a 2 way match. Ken, your new Excalibur team is a good 3 way team, and your new double barrier team is great at the 3 way battle by controlling the battle front. Lance, the first team you played last night was awesome (even though it couldn't do the specific thing you built it for). The second team was fierce mostly because of Wonder Woman. She's just an incredible threat.
So I've been playing around with some armies built to work against multiple opponents (had to reword that sentence 4 times to avoid the double-entendres).
As I was discussing with Lance and Jon last night, I really think in a 3 way fight you want to be very close to the 2 figs per 100 point rule. And having figures with long range support powers (Perplex, Outwit, Prob Control) really helps because you can split your forces and still support each other up to 10 squares away.
I started looking at some older figures and I pulled out some that I really enjoy playing but haven't fielded in a while. We'll see how it works out on our next clix night.
But I totally agree that too few figs in 3-ways seems to be a recipe for disaster.