Hello Jingzhe Wang,

it always comes to what you want to find out in your research. Often the data is resampled to a lower resolution as resampling to a higher resolution might create the false idea that your data is more accurate than it actually is. But if you would loose important information for your study if you resample it to the lower resolution, then you might consider resampling it to the higher resolution. It will take more computation power though... Good luck with it!

I am agree with Dr. Wang. Furthermore, you should take a look to the resampling method you are going to use. Base on this you should also choose which resolution is better for your study. I fairly recommend to explore some of them, if is not high time-consuming process for you. Moreover, you could previously select an ideal resolution for your rasters (should be the same for all of them) and then proceed with the layer stack.

I hope this will help you

Some answers are contained in Gils et al. 2012 and 2013/4

Dear Jingzhe Wang

if we want to re-sample data different spatial resolution, it is better re-sample the data at a lower resolution because the quality and clarity of the image are preserved