2 ETH and which one to use ?

In my server there are 2 NIC cards.
On board is a 10/100 and External one if 100/1000.
Now, total of 10 agents will login.
Should I use 100/1000 for Internet connection or for Local Lan ?
Pl advice.
On board is a 10/100 and External one if 100/1000.
Now, total of 10 agents will login.
Should I use 100/1000 for Internet connection or for Local Lan ?
Pl advice.