Did you know that Steem Dollars pay you an interest when you hold them? So there is an incentive in keeping them in your Steem wallet.
As for buying dips, you can do that using built-in exchange. Usually price is about the same as on Poloniex when you take into account the SBD discount.
So there is no advantage in moving them to Poloniex unless you want to day-trade other coins.
As I understand it, SP pays interest as well along with SBD? The Poloniex market is alot more liquid right now, but Im playing around with both.
Holding Steem Dollar: give true interest.
Holding Steem Power is giving no true interest. You just get partly compensated for the 100% inflation of steem. From this 100% you get 90% back. In away with round about 5% ¨you¨ pay for curation rewards and 5% for post rewards. So if steem grows more then 10% each year and you hold your steem in steem power you win.
Yes, SP pays interest, but it's only to compensate for dilution. If you believe that STEEM price will go up, it's better to keep it in form of SP.
SP pays interest in the form of more STEEM which makes it more like a stock split or stock dividend. It mostly compensates for the very high inflation and (long-term) resulting declining price of individual STEEM token units; most of it is not actually earnings. SBD has a fixed (or at least stabilized) token value so the interest is there "real" interest (variable rate; currently 10%).