I don't have the answer but here are a few ideas...
has a pretty strong dealer network (in the US/Canada anyways), and possibly the best training/certification program for boat engine
And... the brand has a good history
As you point out, Tohatsu now makes the small ones. But I don't myself know whether Tohatsu is building Mercury outboards using Mercury engineering and design, or whether Mercury just said "make us some small outboards".
A big consideration for such a purchase
is - for which can you find parts
in the places you'll be sailing?
(Hey, we have a 1983 Suzuki 5HP that just refuses to quit. It might outlive me)