Big Lab vs Small Lab for Postdoc?
So the question is, big lab or small lab is better for postdoc research?


There is not inherently an answer to this question, but rather plusses and minuses. For example:

Big Labs:


Lots of people around mean it's likely easier not to feel isolated
May have more secure funding
Presumably put out more papers
Professors are more likely to be dealing with keeping that lab funded, so if you were hoping to learn directly from them, this might not be as easy
It's also easy to get lost in a big group and be incorporated into "Professor So-and-So's Group" without establishing an identity


Small Labs:


A larger % of the lab's productivity rests on each person, so there may be more pressure
Might be dependent on a single grant
Likely more personal attention from the PI
More likely to end up as the first author on most of your papers


My suggestion, having been part of labs of all sizes at various stages of my career is to get experience with both, so that you can find what style works best for you and try to pick and choose what you liked from both.