Is Multiplying the Inverse Better or Worse?

Which one is "faster" is indeed a cpu-specific issue, or at least how much faster is CPU specific, yes, division is typically seen as slower than multiplication. And of course all performance questions can be answered with "it depends."

HOWEVER, if you'd asked which is "better" rather than which is faster there would be a clear answer, the more readable one is better. The performance improvement you're looking at is likely on the order of several clock cycles, so unless you're talking about doing this millions of times, you're trying to save yourself microseconds. And there is no microsecond optimization that is worth sacrificing readability and maintainability.

With most processors, it's faster to multiply than divide. But it's really insignificant for most applications, in my opinion you're better off with whichever is more readable, unless profiling shows it's a critical path.

If it's an interpreted language, the amount of time to read the source and convert it to numbers will overwhelm the time taken to actually do the math, especially if you use that many significant digits for the multiply. (Are you sure you really need that many significant digits?)