This assumes I am not mistaken about the 100% SP option and that lots of people won't upvote because you are not doing 100% SP (as @mattclarke mentions in the comments).
Right now getting your rewards 50/50 and not just in Steem Power will give you more power than just taking Steem Power, assuming you get only twice as much of Steem Power as in 50/50. This is because right now 1$ SBD is worth $2 USD so you can trade your SBD for twice as much STEEM and then power it up. This makes 50/50 option give 2/3 more SP overall. Will this continue on to next week? I'm not sure, but right now it seems the best way to be rewarded could be 50/50.