I meant more in ‘opportunity’. Like, casters usually suck when they’re in situations where they’re just throwing out cantrips, and melee fighters suck at times when ranged combat is needed, or when utility/AOE/Elemental spells are needed.
So they can leverage their flexibility to throw 3 actions at the ‘most relevant choice’ between a ‘fighter’ and a ‘wizard’. Granted, either form is going to be weaker than a PC Fighter or Wizard.
Add to that their occasional feats like ‘Tandem Movement’ that lets them kinda sorta cheese the action economy, and things like ‘Eidolon’s Opportunity’, letting the Eidolon threaten spaces even while the summoner is acting more in ‘Wizard mode’, and I think an average effectiveness of 2/3s is fair. Yeah, they do lose out on 2 of 6 actions compared to two full characters, but that just means they dump the 2 ‘least useful actions’ rather than straightforwardly being 2/6th worse.
Personally, I like Monastic Archer stance the best. Not that its the most powerful (probably ranger or fighter is ‘best archer’, in terms of pure archery skill and feats).
But I like monks. They’ll be tankier than a ranger, and have some extra utility and lots of movement. And Stunning fist is great, if not likely to proc all that often. Ki Strike strike on bows is also cool.
And just, having ‘flurry of blows’ leaves you with usually having two actions to do other stuff with on your turn, letting you actually have actions to use other bits and bobs you may get from skill feats, gear, or other archetypes. So you have a lot more flexibility.
So, yeah, fighter will be most accurate, ranger will make the most attacks, but I still like the monk’s ability to dish out decent damage, while keeping the ability to do other stuff in the same turn.