Hi Mammalicious,
I think they're basically the same stuff. I use Calpol because it's what I've always used at home. I have used Panadol whilst on holiday, though didn't find it as effective. It is probably pyschological and more to do with brand loyalty than anything else. As I say I just prefer Calpol because it's what I'm used to. I hope that helps.
I found Calpol really helpful with teething with both my children. We actually say, 'The wonders of Calpol", in our house, once we've given it to them and they stop crying almost immediately.
Jools