Philip Arreola of Milwaukee seemed a model police chief for the 1990's. His 7-year record of working with minorities and diversifying his department won national attention. Arreola, however, left Milwaukee in August 1996 for Tacoma, Wash., where he took a pay cut to command a smaller force. In the face of conflicting forces -- unions and neighborhoods calling for a get- tough strategy, minority groups unwilling to accept a return to hard-line methods and looking to improve their own political standing, and a mayor forced to answer to each of these concerns -- it was no surprise when Arreola packed up and left for Tacoma. If moving too fast is a dangerous strategy for big-city police chiefs, moving too slowly often leads to the same result. Los Angeles Chief Willie Williams, appointed in 1992 in the aftermath of the Rodney King riots, was expected to implement wide-ranging reforms within the entrenched police bureaucracy. Added to this responsibility was another that stemmed from a political promise to expand the size of the police force. When Williams proved slow to deliver on either count, the sniping between the mayor's office and police headquarters grew nastier. With his contract up for renewal in April 1997, the embattled chief's current bargaining position is tenuous at best. In New York City, Police Chief William Bratton managed the police department for 2 years, and was instrumental in reducing crime in the city. His efforts to publicize his achievements fueled conflict with Mayor Giuliani, who wanted a share or all of the publicity for the favorable crime trend. Bratton did not last in New York, but built a reputation that may serve him well in his career development. This has apparently become the reality for many if not most police chiefs. The best hope is to strike for quick results after being hired, make sure they are publicized, and be prepared for a quick exit to another city that wants quick results.