Anyone mentioned anything regarding E34's pipe sound, I will have to agree with you 120%.
I MISS IT BAD!!!!
To the point that I am considering buying a used one again, just for the sound. But a well kept E34 M5 is VERY hard to come by in Ontario. (I saw 2 1993 on the market, one highly modified, one poorly kept

both going for $40,000 CDN or approx $27,000US)
In terms of acceleration, I was able to beat an E34 M5 (probably 1992 or 1991, with the square mirror) with my 1999 E39 540i 6spd, stock to stock, so it's not really in the league of the E39 M5. Even BMW stated that when E39 540 came out. E34 owners, please don't flame me for saying that. I was reporting a past incident.
North America stopped importing E34 M5 since 1993 (I was told, mine was the last to come into Canada), so I didn't have a chance to try the 2-mode-suspension.
I drove my E39 M5 last winter, something I wouldn't dare to do with an E34 M5 (mine had no ASC+T).
IMHO, E34 feels like a SPORTS car while E39, although much faster, only feels like a SPORTY car.
Disregard price, would I choose E34 M5 over E39 M5? Probably not. Spoiled by the E39 interior already, although I do miss the individual armrests over that center console sliding good-for-nothing of E39's.