Still A Matter of Life and Death which I believe is their most consistent album song for song, and also the most focused in terms of atmosphere. I have individual songs I rate higher from The Final Frontier, but as a complete album A Matter of Life and Death takes the cake. (And to be honest "The Legacy", "For the Greater Good of God" and "Lord of Light" are resting firmly in my top 10 in any case.) It's one of those rare albums where specific songs are lifted because they are part of a greater whole - would I listen to "Out of the Shadows" and love it if it had been on No Prayer for the Dying? Probably not! But here it fits perfectly in the flow of the album, and I couldn't imagine skipping it. As for production & playing on the record, I think everyone did a tremendous job on it. The drum sound is a particular highlight for me, and especially Nicko's old snare.
For the record, The Final Frontier and The X Factor are the runners-up.
I can't help but to hear connections in the music contained within. Listen to the riff on BTATS, at around 3:35 (under the solo). Doesn't it remind you of the chorus of LOL? And now, please, listen to the riff in FTGGOG, at about 6:57. Isn't it really similar to These Colours Don't Run? I think so. Maybe I'm wrong, but it helps me to appreciate the album more, so won't convince me so easily otherwise.