If it’s just the fun factor of the operator I‘d say Magallan wins by a landslide. Every skill offers different kinds of utility and a different playstyle. So in terms of versatility and fun she’s top notch in my experience granted, I only get to use her as a support unit :(

Apart from her, Shining does what she‘s supposed to but as a Medic that’s not really anything special (except for harmacist ex-wife). And Lee can be fun to play around with since his S2 has nuke potential especially if you have a multihit op like Kroos Alter or Exu. But his S3 is pretty set it and forget it so in terms of gameplay and fun nothing exciting.

So in summary: Magallan for fun, Lee for fish with nuke (or bully lightweights) and Shining if she’s waifu I guess.