There are too many unknown factors to anticipate what would be best. I suggest you take both pairs of mics and audition each during their sound check. Give a listen and use the pair that best compliments the situation.

Who knows what kind of pre's the foh mixer has? Could be better or worse than your's. But if you use your pre, you will be independant of any undesirable noises and mishaps with their equipment.

FWIW, I have never been satisified with any two mic recordings of groups in a club. It just sounds too distant. Also, the lack of control in a typical club environment usually makes for poor ensemble balance. A two mic stereo recording approach is better than no recording at all. But if you want to come away with something you can really use; multiple mics are the way to go.

I used to use a 2-mic approach for my band in a club, along with a stereo direct out from the main console. It was never perfect, but it at least gave me some control of the band's sound live vs the board mix. (There was always something missing or something too hot, but it worked most of the time.)

If you can do what zilla suggests, go with multi-mics, either for the recording alone, or if you're mic'ing the band for live sound, take separate outs from each channel to a multitrack and mix it all later.

I'd say..

If you only have two channels to work with...and you can't mix them later, and you can't take a submix in the board... then use the Octavas with the hypercardiod capsule (assuming you have one), pointed down slightly, up high, as close as you can get them to the band and still hear the horns of the PA. If you don't have the hypercardiod capsule, then use the c1000's in the same placement.

Otherwise, just run a submix off the board if the board has enough aux sends assuming all things are miced. If you can't do that, run a mono channel from the board for vocal, and a stereo pair in front of the drum kit. The guitars and bass will come out fine.

Basically, the thing you want to avoid is room.