Best way to connect 2 pins that are next to each other?
A large pour would allow more current (just like a wider trace), and would result in a larger solder blob. You probably need neither.

A simple trace between the middles of the pads might look like an accidental solder bridge if you don't know the circuit. To avoid such a misunderstanding, it might be a better idea to route the trace outside, if you can afford the space: