Again, I think charm is the wrong word to describe how Routh is in that scene. It's hard to explain, but I'll try anyway (bare with me, I'll probably make a fool of myself very shortly).
With Routh's voice and delivery, it sorta reminds me more of a 911 operator trying to calm the caller. I'm sure you've heard the tone they use: "calm down sir, everything will be alright. stay with me, breathe slowly, etc." It's more of a deep/soothing type of delivery.
Reeve did it more in a gleeful and corny type of way. Almost as if you'd expect him to say "hehe" in between his sentences, ya know? Like: "Rest assured ma'am, I'll have your son in your arms in no time flat"...all this with a smile. He reminds me more of the authoritative figure that manages to always remain happy in any type of situation in order to ease the people around him.
This is more apparent when you compare the plane statistics line of Routh and Reeve. Even though the line is exactly the same, you'll see that the deliveries are completely different.
Did that sorta explain how I see things? I realize it may be hard to grasp.