I'm used to
Caleb, and I tend to assume
Kaleb in the US is just another creative spelling. Like
Kassidy or
Khloe or Karsyn. If it were pronounced Kah-leb, or the person had some other stuff signaling that he was foreign (surname, accent), that impression would evaporate, and I'd think it equivalent to
Caleb. I prefer the look of
Caleb, and that might only be because it's more familiar.
- mirfak