You will see no appreciable difference. In many/most cases, the >8 (Some 12, depending on SOC) lane boards are all expander-inclusive, meaning that the board has an expander of their own. Going with the higher port count card will save you a slot, will remove cabling from the inside of your case and will in most cases give you more consistent support for the highest speed per lane (Some HP expanders for example may only negotiate SATA150 when they are SATA300 or SATA600, and there is no rhyme or reason with board rev or with firmware version. I have seen it with some Intel's as well)
Thanks for the speedy response...
So I should set up a bit of a test with my 4 x spare 3Tb drives in something speedy like Raid0 ? and test on the card and then on the expander?