While SBD > 1 USD - 50:50 is still the way to go. Don't 100% power up your posts (probably ever).
With the STEEM price and SBD price approaching parity (STEEM is currently trading at $3.76, and SBD at $3.80 at the time of writing this) and, if things continue as they are, STEEM becoming the more valuable of the two (where it should be in my opinion), it may just pop into your head that now is the time to 100% power up your posts.
DON'T!!!
I'm still seeing quite a lot of these (about 5% of people at a quick glance down the feed - that's still a lot) 
, even on posts by accounts with high Rep scores (above 60). You're selling yourself short people!!
Why should I 50:50 my posts instead?
Because you will get less reward if you 100% power up...
The way the post rewards are calculated means that if you 100% power up your post, you will receive STEEM at a rate of 1SBD = 1USD = 0.266 STEEM , instead of the market rate, which is about 1 SBD =3.80 USD = 1.01 STEEM.
This means that if you choose the 50:50 rewards payout option, your SBD can be converted into 3.79 times the amount of STEEM that you would have received if you had powered up that 50%.
The only time 100% power up post works is when SBD is worth (much) less than 1 USD, and even then you may be able to get better exchange prices on the external (or internal) markets.
How can I find out what my reward split will be?
@dragosroua has done a fantastic job of explaining the post rewards calculation process here. If you haven't checked out @dragosroua's steem.supply, this is a good tool to use to see when you will be paid out, and what your expected reward split will be, both in SBD/STEEM, and in USD.
Those of you who are still 100% powering up your posts are losing out on some sweet rewards!
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Well I learned something about how its all calculated from your link. Thanks bmj.
Any time man!
Thanks man, I posted about the same recently again, there's such a huge misconception about post payouts.
It's with the complexity of steem.
New users think power up means more voting power. So they just go for the 100% power up.
We need to educate the masses!! Now that STEEM is overtaking SBD, I have a feeling some will think it's good to 100% power up again... wrong!!!
Sneaky Ninja Attack! You have been defended with a 2.87% vote... I was summoned by @bmj! I have done their bidding and now I will vanish...Whoosh
Appreciate this reminder. As Steem SBD was converging I was just thinking if I should 100% power up again, but I'm glad you posted this reminder why I shouldn't
I don't quite understand this. Could you please expantiate @bmj. These terms are a bit strange to me. Thanks @bmj.
It does get quite complicated to work out. The best explanation I have found is here: http://steem.supply/rewards
Basically, because the way your rewards are worked out, when SBD is worth more than $1 (USD), then powering up your post to 100% will result in a lower reward.