Hi! I'd like to compare expression levels of given genes between two subgroups of the TCGA cohort. I have expression data, derived from the PanCancer Atlas, from cbioportal in two different files: "data_RNA_Seq_v2_expression_median.txt" (RSEM) and "data_RNA_Seq_v2_mRNA_median_Zscores.txt". Which could I use for comparing expression levels between sample groups? Or both of them can be used for this purpose?