It doesn't have all that much to do with the stats.
The fact is that Cath sucks in "siege" rounds, which involve large alliances kicking the crap out of each other on a nightly basis. In rounds where one side wins with relative ease, Cathaar do much better, because they are probably the best race attack-wise, but the weakest defensively (for their inability to kill anything much).
People who expect the races to remain equal in usefulness in every round are denying the effects of the "meta-game", the alliance politics and attack strategies that have a strong effect on the outcome of a round. This round, I'd say 1up are fairly Cath-heavy, but politics has been against them, thus depressing the performance of Cathaar as a race. Exilition have (until recently) been a stronger performer and are fairly Xan-heavy, boosting Xan as a race. Part of this might be
because of their race choice, but it's equally possible that alliance politics are altering the performance of the races.
Your choice of race reflects how you expect the round to pan out - I picked Zik because I (correctly
) anticipated getting a lot of incoming and figured that I might be better off stealing ships from my attackers than going for a massive roid count. If you didn't put any such thought into your race selection, you only have yourself to blame imo.
For those that say "but I always place [race X]!", then perhaps you should consider being a more flexible player? I don't see why the stats should compensate for your inability to vary your tactics.