Congrats! I love the name
Casper (this spelling)! I do pronounce them differently.
Casper =
CASS-purr (cass + the "pur" in purse).
Caspar =
CASS-parr (cass + the "par" in particle). In English, though, this difference is very subtle, and I doubt that many English-speakers would pick up on it. For example, in English,
Shannon,
Shannen, Shannan, and Shannyn are all pronounced the same. I think the same can probably be said for
Casper and
Caspar, depending on the person.
I prefer
Casper. I don't really have a particular reason for liking it more than
Caspar. It's just the spelling I'm used of seeing.