I never saw Van Halen in concert, but I've seen David Lee Roth twice in concert--both were great. I'm not a Van Hagar fan, however I did see Sammy in concert and I was thoroughly surprise at how much I like him solo.
I've seen Van Halen in concert twice: "Diver Down" and "1984". I never heard them complete a song in either show; it was three guys trying to play music and Dave acting like an idiot.
Van Hagar, on the other hand, put on a great concert. It didn't even hurt that much when Sammy sang some of Dave's tunes. Plus, Sammy is a helluva guitarist and it was cool to listen to him jam with Eddie. And despite an hour delay on account of weather, they played the full set anyway. Dave would've never done that.