As Ray and Cam mentioned, sampling is the key. Consider that the details of the object you are imaging cannot be accurately recorded if they are sampled 1:1, but that at least 2x2 and preferably 3x3 pixels should cover the smallest discernible features in the object, given the FWHM on the night. So if FWHM was say 2", then the ideal pixel resolution is 2/3 = 0.66".
Personally I image with 0.87" per pixel. I've found that on 70% of the nights I'm out it seems just right as my FWHM is usually hovering just above 2". On 10% of the nights I wish I had better resolution, and on the last 20% the seeing is worse than 3" and I'd clearly be oversampling (but on those nights I just shoot the RGB, always binned 2x2
).
Others may have completely different experiences depending on local conditions.
I really think the most important thing is to find a good balance between resolution and integration time for the typical objects you tend to image.