Shadow play is by far the most convenient and simple software you'll use. It doesn't kill your frames too badly and can capture the last 5/10/15/20/25 minuets of gameplay. I do get a frame crash when I do record the last 15 mins however it lasts a few seconds and is fairly minor. (Only for NVIDIA GeForce GPU's I do believe)
other than that, correctly configured OBS x64 is good for free software, however you'll need to be a little more advanced than shadow play.
All the real good ones need to be paid for.