Well, this is another cruel thread but I've arrived at my verdict. Choice #1 is easy because it's my favourite Zep, but for choice #2 I had to sweat a bit to arrive at a satisfactory conclusion. Physical Graffiti + IV
Believe me, you would understand after the nth shouted repetition of Hey whoa where the wind don't blow really shouldn't go it only goes to show a whoa whoa whoa ride the wind gonna see you spin gonna shake little girl bop bop a shoo ah everybody I know shweedle hamma hamma blow anna ramma whamma ding dong hoo la hey I didn't start listening to Zep again until 1987.
Just due to variety, the great sequencing, and the fact that I could have at least a taste of every album... Led Zeppelin 1990 Box Set: Disc One Disc Two Disc Four