The comparison of two fine-tuning strategies suggests that the simpler FT-DIRECT fine-tuning has an edge over FT-MIXED, and it seems that the gap between FT-DIRECT and FT-MIXED is larger on bigger datasets.
as expected, FT-DIRECT adapts to the target task more aggressively: this leads to its degraded performance on the general-domain Reddit response selection task, see the scores in parentheses in Table 3.