Fun Fact: Arbitration and Lespia Aureus deal has a same cost but time difference.

Both of them cost -4B, but Arbitration costs happen in Turn 6-7 with -2Bpt modifier and +4Ept, while Lespia Aureus deals costs -4B during Turn 4 with +2Ept later on.

Lespia Aureus has 2 positive effects which gives only +1 negotiation power in Wehlen trade and +1 Lespian relation, still being them friendly in the end is not worth it since you have to sabotage MITZ to achieve that, make Lespia neutral in the end.