After some serious thinking, my votes is for Let Me Put My Love Into You!
I greatly like all three of these terrific songs!
The excellent blues riffs in the beginning of Feels Good reminds me quite a bit of earlier, bluesy Sabbath material.
Slow An' Easy is both one of my favorite Whitesnake songs, and definitely rocks!
Imho, Let Me Put My Love Into You is one of the top songs on Back in Black!