It seems pretty clear from RAW that for many characters your effective dexterity when pinned is higher than when merely grappled.
This is because the grappled condition applies a -4 Dex modifier to both the controlling grappler and the controlled, but then the pinned condition removes the penalty from the controlled grappler. In place, it removes their Dex bonus.
I think this has some weird (but corner case) effects.
Someone with poor dexterity might prefer to pinned than grappled when there's an incoming fireball.
Someone with the feat agile maneuvers, and dexterity less than 14, and intending to escape or reverse a grapple, would prefer to be pinned rather than grappled.
(There's really a not of things you can do with your dexterity when pinned, so it really is corner-case stuff)
So my question is ... have I missed something foolish?
Or does this need (a very low priority) patch?
e.g. apply a -4 Dex penalty to the pinned condition in addition to the loss of the Dex bonus.
Relevant rules below -
From the glossary:
[...] Grappled creatures cannot move and take a –4 penalty to Dexterity. A grappled creature takes a –2 penalty on all attack rolls and combat maneuver checks, except those made to grapple or escape a grapple. [...]
http://paizo.com/pathfinderRPG/prd/glossary.html
[...] A pinned creature cannot move and is denied its Dexterity bonus. A pinned character also takes an additional –4 penalty to his Armor Class. [...] Pinned is a more severe version of grappled, and their effects do not stack.
http://paizo.com/pathfinderRPG/prd/glossary.html
From the FAQ:
When a creature is pinned, it gains this more severe version of the grappled condition, and the two conditions do not stack (as described in the pinned condition). While this means that you do not take both the penalties for both the grapple and the pin, this also means that pinned supersedes the grapple condition; it does not compound it. For this reason you only need to succeed one combat maneuver or Escape Artist check to escape either a grapple or a pin.
http://paizo.com/paizo/faq/v5748nruor1fm#v5748eaic9o3t