Will take all this period, the first couple DLR records and all the Van Hagar albums, all of them still regular plays although those Roth and first two Hagar records all in desperate need of remastering...
In respect to the OP while 5150 would probably take the win for nostalgic reasons, these days OU812 is my preferred Van Hagar and has been for a long time. The heavy hitters are where it's at, Mine All Mine is the perfect opener, both Sucker and AFU are magnificent and agree the take it or leave it Source Of Infection actually works surprisingly well. Of course love the kicking back Cabo Wabo and Black And Blue, neither have lost anything over the years and gotta shout out for the I'll Wait throwback of Feels So Good which often gets looked over albeit a sensational tune it is and deserves a look in. In fact my least liked song is the usually much loved Finish What Ya Started go figure.
So for arguments sake ranking 5150 and OU812 equal and both essential. I'd then put F.U.C.K. slightly ahead of Balance, the former the more complete but somewhat one directioned album (Judgement Day was IMO worth the price alone however) and the otherwise great Balance slightly behind due to too much filler (Seventh Seal and Aftershock however two of the best Hagar era songs, and Lordy me how great an album would it have been had they managed to write and include the very epic Humans Being and closed the album with the Japan bonus track Crossing Over right?)
Anyway yes, still enthusiastic with OU812