though the risk of a noodl-y mess is very very real, I'd say that the node/wire handshake is direct perception of data & action flow
the connectors remove the cognitive load of keeping track of what effects what in 2D space -- so my inclination would be to draw them always
also, if a user draws some but not others, that inconsistency is even more cognitive load, where the legibility of the graph now depends on a previous builder (or even yourself 2 months ago!) making the right choices in terms of which connector to manifest