I say Hobnob's plan is better.
Hobnob's plan is Kayden's, which is probably a good idea. Cassilda's is as well, however. From what it looks like so far, I will flip a literal coin lol. On the one hand, they'll let the Lord die (but also lose a valuable friend in the city) but get most of the bounties and capture the keep, or Kayden will probably lead the majority of the group to the keep, and a skeleton group of volunteers will probably flank the attacking 30 while they're engaged with the Knights...and get most of the bounties and capture the keep.
The main difference is, do you want a Lord to be friends with you, or do you want the shit he's shipping?
Also, Kayden never said they'd storm the keep. wink wink nudge nudge. Did someone say, secret passage? He never mentioned it IC because not everyone has agreed to be in the team yet. Can't go out handing this info to anyone