The downside to delegated Steem Power is that the one giving you the steem power gets the curation rewards for that power... So your old account would get the curation rewards. In theory if you had enough accounts that you had loaned steem power to and they had the lions share of your total upvotes on the post you could essentially get 100% of the rewards this way. If I were a whale I would try to spread my steem power around to as many people as possible especially promotion bots as this would be fairly healthy returns.