I'm new to Siri upgraded from a 4 and now have it on my iPad. I thought it was interesting that each one sounds a little different and even pronounces words differently. My iPad will say kinda (kind-a) and my phone says (kin-da). Just odd.
Have you checked the language localization? Might be some different pronunciations in the software depending in that.
Weird... I noticed that Siri on iOS 6 does sound a bit more robotic than on 5.1.1 but not sure how two devices on the same software would have different quirks.
My Siri seems to have some psychiatric issues. It will change pronunciations of words but with the same spelling. i will say "Call Name A." Siri will respond, "I can't find Name A but would you like me to call Name A?"
What is shown on the screen is the same name both times but, for some reason, Siri pronounces the first time differently than the second time.
I've had this happen several times. It gets a little annoying because I do this dance with Siri getting it to acknowledge a name, a song, an artist, etc. while all the time the written form on the screen is the same as the challenge but the spoken is different.
So, Siri is gaslighting you?