Hmmm... does it work like Rich mulch (which was a set +2 berries), then, or more of a ratio thing? (Like, increases yield by 25-33% (rounded down)) Either way, it's still probably the better one to go with given our time scale.
Note: I'm assuming that Less won't want to delay going to the Spectral dimension for long enough to really get the benefits of multiple extra crops over just having bigger ones. Also that Mark doesn't have the charisma to convince the group grandpa to wait a bit for gardening.