Apple :: Why 10-point Calibri In Word 2008 Looks Like 15-point Calibri In Mail

Weird question, but: why is it that in Apple Mail, I can set an outgoing font to 15-point Calibri and have it look identical to an incoming Office 2007 user's message sent from Outlook (and in fact, "show fonts" shows it as 15-point Calibri), but in Word 2008, if I were to set it to 15-point Calibri, it would be huge compared to what I remember it as in Office 2007?

Its default in Office '07 is 11 point, if memory serves. To my eyes, 10-point zoomed to 150% looks normal, but I definitely do not remember this.

Is this just a function of OSX's 72 dpi versus Windows's 96 dpi? I'd hate to send an email at 15-point Calibri, have it look like an 11-point Calibri message in Outlook '07 on the Windows size, and end up having my recipient get an email with a HUGE font.

I've looked at messages I've sent using 14- or 15-point Calibri in Outlook 2010 in Windows 7 via Boot Camp, and it looks like I'd expect 11-point Calibri to look.