If paytaxfee is 0 by default does it make sense then to use -sendfreetransactions and would the second option isted of the default 0 fee have any sort of performance impact on a system with large number of transactions per second.
-paytxfee=<amt> Fee (in BTC/kB) to add to transactions you send (default: 0.00)
-sendfreetransactions Send transactions as zero-fee transactions if possible (default: 0)