The OP and the post above touch on the main advantage a max power .357 has over other commonly used pistol calibers, more penetration (assuming suitable slugs), more energy at all ranges with the advantage increasing with range and a flatter trajectory (probably not significant in 98% of LE engagements).

Having said that, I think most LE would be better served with today's semi autos. There certainly are those who master revolvers but doing well under stress shooting DA with a revolver I think is far harder than getting good hits with a Glock, 1911, Sig, etc. Don