Which is actually funny since everytime I travel by DH8, I only have 1 flight attendant :-)
Anyway, based on the chart I use to choose my planes, the ATR is slightly consuming more than the DH8 per travelling passenger per nautic mile. (ATR 72-500 is 0.01229 whereas DH8 is 0.01115). Therefore, DH8 burn slightly less fuel than ATR.
However, they cost you an average 19 257 $ for maintenance checks per week whereas the ATR is 18 440 $ per week. This figure includes the average payment for the four checks over a period of 7 operating years. If you remove the D checks, the ATR is still a bit less expensive on the long term (14 728$ weekly against 15 380 $ weekly for the DH8).
If you plan to have a plane flying longer routes ( about more than 600nm), you should definitely go with the DH8. If you plan shorter routes, the ATR is fine since you have less maintenance costs incurred and the fuel consumption difference will not break even.
Hope this helps