Use Merge when experts already exist and cheap fusion is paramount; Mix RL when training a unified model without experts; and MOPD when preserving domain-specific gains matters more than surpassing teachers

use Merge when experts already exist and cheap fusion is paramount; Mix RL when training a unified model without experts, with domain proportions adjusted for cross-domain transfer; and MOPD when preserving domain-specific gains matters more than surpassing teachers or minimizing end-to-end cost

http://arxiv.org/abs/2608.27409v1