I recently got a Montane Litespeed and a Patigonia Houdini, both in size Large, to try them both out.
I'm 6ft, 195lb, 42in chest. The Litespeed fits true to size, and the Houdini seems a little larger. With my Montbell inner jacket and a t-shirt the Litespeed will compress the down jacket across my shoulder blades when stretching my arms forward. The Houdini however doesn't affect the loft when I stretch/contort my posture.