Without your being able to try them in person, this is a very difficult decision. I haven't played the cabs in question, but they may sound a good bit different from one another - and without taking your tonal preference for each into account that just leaves us with nothing to decide on but posted specs.
So then, without further ado, let's do just that!
As long as you're planning on running two of these, I'd say that the power handling shouldn't matter. Any two of those CX cabs should be more than adequate enough to handle the power from your 700RB-ii.
Next up: weight. 67lbs is pretty heavy in my book - at least nowadays. I remember back when moving a 70lb 210 was nothing... but now 70lbs definitely is something to me. And maybe to you too. Personally I'd rather move two sub 40lb cabs than one 70lb cab, but I know others that feel the opposite is true.
So in my opinion, that leaves us with the 210s and 115s.
They're both the same size, so the primary trade-offs appear to be in the departments of:
-weight
-efficiency
-extension?
-dispersion?
The weight difference of 35 vs 37 pounds isn't that big of a difference.
By the published specs the efficiency difference between the two is enormous, but GK has admitted to me that the published efficiency specs are likely wrong. From GK, the 210 is rated at 99dB, with the 150 probably around 98db.
As for extension, I'm not sure how much the GK specs can be trusted due to the efficiency confusion noted above, but the 210 extension is rated from 53Hz to 18kHz and the 150 from 51Hz to 18kHz (same as the 410 FWIW). IME these specs are usually pretty meaningless when it comes to how a cab actually sounds.
Lastly, dispersion. Given that the 210 uses the diagonal arrangement to make sure they can fit into the same size cab as the 115, there's no real way to stack them to get the drivers to align vertically. With 115s you can. Will it make a meaningful difference? Any difference at all? Who knows, but just calling it out.
So with all that being said I'd say that a pair of 210s might work slightly better if you're trying to maximize the volume from your 700RB-ii as the sensitivity is slightly better.
If not, I'd seriously consider a pair of 115s. They weigh less, may have a slightly better dispersion pattern when stacked, and if you ever get crazy and damage your cabs, it'd be less painful to replace two drivers vs. potentially 4.
Good luck with the decision!