the p410i has throughput problems with sata drives and the p410 add-in card does not. So as far as i can tell there's some difference between the two.
As you can see the average throughput is low compared to the onboard and it's very bursty. This is the same 3 drives attached to the onboard p410i - same raid configuration, internal bays used and benchmark configuration. the write test is 1mb block size, 100% sequentual writes test using iometer (1 worker). the 350mb/sec is around what you'd expect for this configuration.
This is attached as a non boot drive so that there's zero io going to it except the testing. This is the transfer rate using iometer when attached to the p410 add-in card (3 x 1tb hitachi drives in raid 0, 256k stripe, 75%/25% write/read cache ratio, Drive write cache enabled). The server runs fine using the 300GB SAS drives but using SATA drives (the below benchmarks apply to the WD 750GB scorpio black (WD750BPKT) i get low transfer rates compared to the p410 add-in card. I have a HP D元60 G6 with an onboard p410i controller and have some problems with the performance of exactly the drives you're thinking about using - HGST Travelstar 7K1000.