So I wrote a letter to S&W if they updated their triggers and this is what I got:

REFERENCE NUMBER: LTK51404006498X Please use this ticket number in any correspondence with us.
SUBJECT: New triggers

Dear Customer,

They have a different trigger in the M&P Shield only. They have not updated the triggers on all of the other M&P's.

If further assistance is required please reply accordingly.


Sincerely,

Don



So for what it's worth, I guess it's depending on the individuals comfort level and their own tastes in triggers. Hope this helps ease some curious minds.