Having been in a past life involved in customizing police helicopters . I can tell you that the people who select the mission equipment often have little real appreciation of the weight they are adding. I must say the salesmen , who should know better do not always advise the customer well.
To compare apples to apples you should see how much useful mass ( above basic weight of minimum equipped aircraft plus pilot and fuel ) each helicopter can lift on a 20 deg day. Even though the 206B3 does not have crash attenuating seats ( that add about 200 Lbs to basic weight ) . That said the 120 has useful load 97 kg greater than 206 with c20B hover OGE at 2000 meters and isa +10 but 18 kg less at 2000 meters ISA +20 according to manufacturers charts ( in the marketing info ). The 206 manual does not list weight of crash attenuating seats , though I think they are fittted to the TH57 .