As piston helicopters go, it is darn hard to beat the Enstrom. Only 9 life limited parts and no major inspections (1200 or 2200 hr) required.
First I would take a careful look at the Type Certificate Data Sheets for each and the ADs for each. Especially the recurring ones. Then get a little time in each to see which ones work best for you. Many like flying the 500, it is a nice handling machine. The Enstrom and the 206 have probably the best safety records out there. As for fuel costs, the 500C and 206B2 will have fuel costs that are close to the 280FX's.
As for the 480, the seating is not as comfortable and the value for money is better on the 500 and 206.