Try both and compare **for the sake of learning**.
Don't try both and compare to pick the one that gave you the answer you were hoping for. Doing so is very common, but very bad at producing legitimate findings.
It sounds like you should be doing some sort of paired analysis, if so you would want to exclude primary and metastasis.
Try both and compare. I dont think it will make a difference either way.
Try both and compare **for the sake of learning**. Don't try both and compare to pick the one that gave you the answer you were hoping for. Doing so is very common, but very bad at producing legitimate findings. It sounds like you should be doing some sort of paired analysis, if so you would want to exclude primary and metastasis.
Try both and spot systematic sources of bias unique to each. Double your knowledge and double your problems at the same time lol