I feel that in most cases it's the opposite. In the 6spd it might do the 6-5-6-5 shuffle, but in the 8spd it can contently stay in 7th (or 6th or whatever is good for the grade). With the added ratios it's more likely to keep the engine in the desired range. Plus, the paddle shifters make it super easy to make those shift limits when necessary.I've heard that they [2016+ 8spd] hunt for gears a little more too.
I do, however, always drive in manual ('sport') with 6th set as the max in town. The economy bias of the 8spd bogs it down too much for my liking. I won't allow 8th unless over 60mph.
They (at least the LX) need a Pedal Monster to liven it up, but there's no perceptible change in acceleration.The later models with the 8 speed (2016+ I think) are a little slower than the previous years, but still faster than the hundy.