@Zephos:
Higher power blurs the theological lines nicely, since I'm pretty sure there is no major religon that influences Sanji let alone 90% of the cast.
Yeah; we really don't know that much about religion in One Piece seeing as how we've only seen a couple references to it with the single biggest reference being Bartholomew Bear and the various local deities of Alabasta.
The only other reference I can really think of off the top of my head is that we get a glimpse of the Lyneelian Bible at one point, which may even be where Bear is from.
Asking Zoro about God doesn't really make sense anyway seeing as how he's Japanesque in origin. If he believes in anything, it's less likely to be a montheistic diety than whatever the Odaverse equivalent of Shinto or Buddhism is. It's not like Sanji knows what religion, if any, Zoro is as I can't see them sit around discussing such things.
Of course, the primary reason for the switch is to avoid having Zoro tell Sanji that believing in God is silly. Hell hath no fury like a bunch of fundamentalists that apparently have nothing better to do than complain to the FCC.
If Bartholmew Bear says Higher power, then bad.
Depends on context actually.
If Bear says, for instance, "I serve God" to a World Government official somewhere down the road, Viz turning that into "I serve a Higher Power than yours" is entirely appropriate. But in most cases, God would work better though.