I preferred season 1.
Season 2 had some fun supporting characters, but I found Molly Solverson a more interesting protagonist than her dad and Lorne Malvo was a far more scary and charismatic villain than the Native American hitman/helping hand in season 2. Season 2 was still very good, but nothing in it happened which I found as surprising as some of the plot turns in the first season. I thought that leap one year ahead in season 1 and what happens then was absolutely brilliant. Season 1 had some genuine "holy shit" moments which season 2 lacked. The UFO in season 2 was sub-Twin Peaks quirky-for-the-sake of it stuff I could have done without. And the massacre in season 1, all shot in one take from the outside of the building, was the outstanding sequence of either season.
Kirsten Dunst was good but the parody of 70s semi-feminist self-actualisation was layed on too thickly. The incident of a hit and run, where the woman drives home with the still alive victim embedded in her window, was based on a real case and has made it into several films and TV series by now. The murder of the traitorous granddaughter in the wintery forest was too reminiscent of Adriana's death in The Sopranos (maybe the most upsetting scene in the entire series), but not as memorable.
The character I found the most interesting in season 2 was Jean Smart's gangster matriarch who looks like your friendly, cookie baking gran but who is tough as nails. She got dispatched rather unceremoniously I thought.
Not a criticism, but rather than the Coen Brothers own films, season 2 felt heavily inspired by the 70s rural gangster film Prime Cut with Lee Marvin and Gene Hackman. It's a favourite film of mine and jawdropping in its political incorrectness, but that's also what makes it great pulp fiction.