Roughly equivalent would be a good description, it also depends on how good the avr is with blending the surrounds into the rear channel and vice versa. I ran 6.1 in my old house. I chose this due to the fact I had the TV in a corner and the side surrounds were mounted in odd positions which left a rather large hole in the surround field, adding the sixth channel(no room for a 7th) really filled in the gap and gave me a nice surround experience.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70