Why a K1 visa instead of a K3 visa?

Why did we decide to apply for a K1(fiance) visa instead of a K3 (spouse) visa? It was essentially decided by the fact that my fiance is adamantly opposed to living apart for any length of time after the marriage. In the long run it may not take any less time for her to become a legal permanent resident of the U.S., but if we marry in Japan she will have to wait in Japan while her K3 visa is processed.

It's true she has to wait in Japan for the K1 to be processed but there are some important differences. First is the psychological difference, but there also seems to be a very real difference in processing time. Because I live in Colorado most forms are processed by the UCSIS Nebraska Service Center, including the I-129F, but for some reason I-130's (for K3 visa's) are processed by the much busier California Service Center. Using the processing times given at http://www.visalaw.com/ it would seem that there is a difference of approximately 5 months in processing time.

The uncertainty of the whole process already has me uneasy. The I-129F is just the first of a multitude of forms that need to be filed and who knows what the penalty for the slightest mistake may be.