The first (https://jacksonupperco.com/2014/07/08/the-ten-best-the-mary-tyler-moore-show-episodes-of-season-one/) two (https://jacksonupperco.com/2014/07/15/the-ten-best-the-mary-tyler-moore-show-episodes-of-season-two/) seasons featured Mary as a real pushover and lots of Rhoda while the final (https://jacksonupperco.com/2014/08/12/the-ten-best-the-mary-tyler-moore-show-episodes-of-season-six/) two (https://jacksonupperco.com/2014/08/19/the-ten-best-the-mary-tyler-moore-show-episodes-of-season-seven/) seasons featured a more assertive Mary.

As with most series, I usually prefer the earlier seasons (Mash, Andy Griffith, Law & Order), but after watching the last MTM season, it is a really strong season, all around.
The show lost something when Rhoda left. Georgette wasn't really a "replacement" for Rhoda. Still, that last season was highly humorous.

As far as how Mary was, I loved both the early seasons and the latter seasons of her character equally.

As a whole, I prefer the earlier seasons because of Valerie Harper as Rhoda. The show didn't miss a beat when she was spun off, but I still felt like the show lost a little something with her departure.