You will see no difference in speed if both cards are running at the same transfer rates. So say your onboard is 10/100 and your PCI card is 10/100 no one of those is superior over the other.
If your onboard though is 10/100/1000 I would go with that since you will have gigabit capabilites if you ever decided to implemenet it
I didn't mean it like that. What I meant is, will onboard lan use more CPU resources than a PCI? I heard that onboard devices lag on system resources more than PCI devices, because PCI devices do the processing themselves.
I also heard that PCI is usually more stable than onboard.
You will see no difference in speed if both cards are running at the same transfer rates. So say your onboard is 10/100 and your PCI card is 10/100 no one of those is superior over the other.
If your onboard though is 10/100/1000 I would go with that since you will have gigabit capabilites if you ever decided to implemenet it