I've always found their availability to be pretty much the same. Skyteam does seem to have less of the "reserved for our own elites" and "preferred relationship" business going on than Oneworld. One thing you might want to consider is the ability to redeem on non-Skyteam partners (DL: Singapore Airlines, CO: Qantas). If you're just looking at a straight Skyteam redemption, I would probably transfer points to CO, because of their better search engine (and the resulting higher likelihood of being able to book an award online), and because of the ridiculous DL fees (you are fairly likely to run into their $25 phone ticketing + $25 partner award fees).