Except that Phiona can't use Power Tokens, costs more, doesn't have a 2" engagement range, doesn't have Scatter, doesn't have Toss.
I'm sorry that I keep going on about this, but I started this thread complaining about how one dimensional Hoffman is and the consistent argument from a number of folks here has been that to be successful you need to lean into that single dimension of play. Which is just completely contrary to my experience with the game. I have always found that you win by bringing a diversity of tools to the table that allow you to respond to different situations, that movement tech is very often what wins games.
The Peacekeeper is a never-take for me because all it brings to the table is murder, and I rarely need to kill more than a model or two all game (sure, I'll kill more if I have AP free as insurance). There are plenty of ways to do that. The Guardian on the other hand effectively frees up a ton of AP for scoring and unlocks otherwise impossible positioning.
I will grant that Hoffman (with the Transfer Power pushes and access to lots of Fast) can cope without the Guardian's tech. But he also has a beastly damage track so I'd contend he doesn't need to spend all his stones on dedicated beaters either.