CDO

Assuming I have 2 separate netCDF files with each of grid size 0.5x0.5 degrees and 0.25x0.25 degrees respectively. What I want to do is convert them to same grid size so I can perform raster calculations and comparisons easily.

Can this be done using CDO or any other method which is scientifically acceptable (as increasing or decreasing grid sizes using certain methods as bilinear, cubic interpolation, etc or whichever is best)?
Is it good to change 0.25x0.25 file to 0.5x0.5 degrees or vice-versa?
I am kind of confused with the remap feature of CDO. Can someone please provide an opinion?

Thanks in advance.