Generalguy, please don't talk without experience. BeachBoy and I don't "lose to the more competitive teams". Offensive teams cannot be walled effectively, breaking pure stall. You can still cover offensive threats with a team of six sweepers.
I personally think that balanced teams cannot function well offensively or defensively. Either you go an offensive route or a defensive route - with the inclusion of stronger sweepers that can overwhelm a defensive force, particularly with high-powered moves like Close Combat, the physical special split and Life Orb, I find it hard to rely on a few walls to make up the bulk of your defence. I personally think that with a balanced team you would have trouble trying to cause and wall damage, I doubt you could fit a Spiker/TSpiker for instance on a balanced team due to the intense competition for a team slot adding on to the fact that most Spikers do not cover as much as opposed to another wall and such.
I highly doubt that BeachBoy loses to the "more competitive teams", he is a solid player by my experiences battling with him (always win 1-0 for some reason =P ), and his team can cover the necessary threats while posing a threat itself.
EDIT: Maybe you could substantiate your opinion by giving examples of what an offensive team cannot handle that a balanced team would?