FWIW. Depending on the situation where you are (specifically, eBay), it might be slightly better (more economical in the long run) to look for an Ultegra crankset because:
- the Ultegra chainrings are better (i.e., nickel-plated == longer wearing)
- the Ultegra crank comes with self-extracting bolts
In North America, the price difference (new OR used) isn't very large (or, not as large as the cost differential for the rings & bolts ... way-back-when, when NEW, the difference was only about $20US [the cost of the self-extracting bolts, alone] & the chainrings probably cost 50% more) -- so, the 105 Octalink crankset is is one of the 105 components which isn't the bargain one might presume or hope for.
I've got an
unused 105 Octalink BB as a spare in my toolbox, so I cannot tell you if it is signifcantly better-or-worse than the Ultegra/DA bottom brackets, but my reckoning is that the difference is mostly cosmetic (and, cost).
I actually prefer the
112.5mm XTR Octalink because it means I can readily move between a double & a triple crankset (a discovery made through laziness) whereby I only need to adjust the front derailleur's inner stop (after switching cranks, that is). The XT & LX Octalinks have a different spline pattern, in case you were wondering.