Definately stay in the law enforcement job. If you think back to your first few years on the job when everything was exciting and new and you loved your job, that is how you will feel again when you take the airline job. Then when the reality of trading your 70k a year police job for a 30k a year FO job hits, you will like flying less. After your first year of reduced rests, lousy schedules and being away from friends and family for days on end, you will like your new job even less. The airlines take ALL (well almost all) the fun out of flying and it becomes little more than a job.... much like your at now at the PD.

My advice; stay at the PD, keep the seniority you have in this unstable economic times, enjoy a good Govt job with full benefits and retirement, and fly for fun on the side instead of working that extra detail or overtime.