These figures illustrate the different types of war fought in each theatre.

Ambush and sudden death awaited the careless or unlucky because it was often impossible to see more than a few feet into the undergrowth. In the Southwest Pacific, small arms claimed 32 percent of Americans killed in action during the war and artillery 17 percent--a marked contrast to the overall rates in the European theater of 19.7 and 57.5 percent respectively. In part the aberration stemmed from the relative paucity of Japanese artillery compared to their Axis allies; in part it reflects the face-to-face combat characteristic of jungle fighting.
http://www.ibiblio.org/hyperwar/USA/...nea/index.html p. 9