Ah, another situation in which there might not be a "better."
If you need to set the spacing of graphics and text in
combination, it would be best to be using the same measure (pixels)
throughout. In addition, points and inches are more old-school
(printed documentation), whereas pixels are better interpreted by
Help viewers (hh, browsers, etc.).
However, your ultimate solution will speak to your own
comfort zone, which only you can determine.
Good luck,
Leon