IMO, the best side 1 of all the JP albums to date belongs to Screaming For Vengeance (SFV); with the best 1,2,3 punch of Hellion/Electric Eye, Riding On The Wind & Bloodstone following with a terrific (Take These) Chains and closing strong with Pain & Pleasure. Shoot, even side 2 is perhaps the best side 2 of JP's catalogue - SFV, You've Got Another Thing Comin', Fever and Devil's Child - this album is strong all the way through.
Now, British Steel (BS) and Painkiller are very close and strong as well; I would go with  BS as having the best side 2 of the JP albums - You Don't Have to Be Old To Be Wise, Living After Midnight, The Rage and Steeler (the best closing song out of all of JP's albums).
Painkiller is great too and was tough to put 3rd; Painkiller and All Guns Blazing are so strong that these 2 songs alone put this album as one of the top 3 best side 1s, but with BS opening with Rapid Fire and Metal Gods, then going into the big hit Breaking the Law, with the awsome Grinder and anthemic United closing out the side, you have to go with BS at #2, and really close to being #1.
This my opinion. What is yours?