You could use whichever you're more comfortable with and nothing will happen either way because the brackets are already hitting the stud in two locations. The two non-stud anchors on each bracket are really only there to stop the bracket from flexing/twisting under the weight. I personally like EZ Anchors because you just screw them into the wall where you want and are done. Toggle bolts are very strong but definitely more tricky to do through TV brackets if you've never done something like that before.

To put your mind at ease, I have a 30lb articulating mount on a 100lb TV and only use four screws for the entire thing and my bracket can come out almost 2 feet. Now they are lag bolts (thicker screws) but if you're using the flush-mount samsung kit you're looking at maybe 50-60lb total for the TV and the brackets are maybe 2-3lbs on an install that never moves. You could probably fire two 3" deck screws screws into the middle of each bracket on the stud and the TV would never move. Don't do this, but I want to make you more comfortable with the amount of support you're throwing at this TV with 4 75lb anchors and 4 stud-screws.