Hmm... not too sure why you discard a well scaleable and proven solution like DataServices.
Concerning SQLDBC: that's just another API (for C++ in this case) to communicate with SAP HANA. It's not "more native" than the JDBC driver in that sense.
The most prominent source of information on SAP HANA technology would ... here on SCN 
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Besides all that: when you consider high volume data transfer it is important to think "parallel".
Serial data transfer always only ever scales to the limits of a single thread and what the network interface can provide you in terms of bandwidth.
- Lars