I love programming stuff and it's even more awesome if it is actually helpful to other users and used by them! I am an Austrian ;)
The difference between RC and HP is, RC is used for creating transactions on the blockchain. The more (and the larger) txs you create, the more RC is used. HP on the other hand says how much VESTS you have put in your account. So it comes with other benefits, such as rewards for authoring and curating posts, for voting and all kinds of other stuff. RC is actually a "part" of HP and directly related to it - the more HP you have vested into your account, the more RC you have.
So to answer your initial question - I don't think any of the curation services you can delegate to provide rewards for delegating RC, as they won't get any rewards from that either. It's purely used for being able to create transactions on the blockchain. So RC delegation is more for supporting new users or services requiring a lot of RC, as they are creating lots of transactions.
It will still make sense to delegate HP to "curating" services, as they do the hard work of finding quality posts and you won't have to do that yourself. Usually also the reward for curating / voting will be larger for small accounts with not too much HP if they delegate to such services paying out rewards, as small votes (dust votes) won't give the same reward. There are some kinds of thresholds for that I think.
Thank you very much for clarifying my doubts, thanks again for the excellent information.