I'm going with Slip of the Tongue. Admittedly, it's not their best songwise, but I just cannot deny the presence of Steve Vai. He is someone that turns 'good' into 'fucking majestic'.
"Slip of the Tongue" - sweeping appregio harmonics in the verse riffs?
"Cheap n Nasty" - one of his best solos ever, ending with that tremelo flutter
"Fool for your Lovin" - yep the remake was better IMO
And of course, the fucking epic Whitesnake tune of all tunes, "Sailing Ships". Just an unbelievable performance from Coverdale - probably the best I've ever heard him sing.
Good album, good memories, Vandenburg's arm problem was bogus, so the conspiracy of "hired gun" Steve Vai makes it all the more memorable, heh. The headline performance (with Aerosmith) at Donnington in 1991 had Vandenburg back in the mix trading chops with Vai on stage...have that on tape somewhere since Radio 1 broadcast the show in FM.
Oh and it was a 7 String Ibanez on that album (with coral sitars and Eventide Harmonizers) when the Korn kids were still just an itch in their daddy's crotchless panties.
Steve Vai > everyone in the universe (except maybe Randy Rhoads, and a few others, and that flamenco guy...yeah)