I'll start with my opinion.
I'm not a fan of the way the records sound during Phase 1. The drums mostly lack balls (except for The Black Album), which is a massive deal breaker. Also, AJFA has no bass, which is sacrilege in the worst way possible. Not only can you not make a record without bass, but a metal record???? Unacceptable to me...
Now, phase 2. I'm a big fan of hard rock, and Metallica's sound was lends itself very nicely to the songs on Load & Reload. As a plus, James' voice is at a peak. Then, St. Anger isn't so comparable to Load & Reload. But, it's a KILLER record to me. I was one of the St. Anger deniers, until I watched the documentary "Some Kind Of Monster". Understanding where these songs came from really made the glued the whole sound together. Since then, I've really been enjoying the record, despite some songs dragging on for just a bit too long.
Phase 3 is a different kettle of fish to both phase 1 and 2. Despite their return to their thrash roots, Metallica's Death Magnetic gives you an entirely different feeling to the first records, since the sound is so different. It does sound a little lower quality than what came after, but it remains a record I'm a fan of. Hardwired... to self-destruct however, is one of Metallica's best records, if you ask me. Maybe the songs can get a bit samey, but James once again sounds absolutely awesome and now, the production is on a whole other level. 72 Seasons, which followed, came in and expanded Hardwired in my eyes. Not much that feels very new, but it remains a great record.
So, based on all this, I'll have to go with phase 2. You?