I test drove two used E70s last week, one 3.0i and one 4.8i. I think going from 4.4 to 3.0 you will miss the power. The new 3.0 definitely feels (and is) faster than the E53 3.0 that I have, but not by much... I can not justify going from my 3.0 to an E70 3.0 as an 'upgrade'.
I really think that the diesel would be the best way to go though... torque is all that most of us need, and it has plenty of.
I did not test drive it since they didn't have any, but from what the salesman was saying, it definitely has more acceleration than the 4.8i.