RNA sequencing provides quantitative data on arbitrary transcript abundance, while microarrays only detect predefined transcripts

Microarrays rely on hybridization to complementary probes, while RNA sequencing uses direct sequencing of cDNA

Both RNA sequencing and microarrays generate  raw data that, analyzed with the proper bioinformatics tools, provide information about arbitrary sequences on the sample. 

Microarrays can detect novel transcripts not included in the probe design, whereas RNA sequencing cannot

RNA sequencing has a higher dynamic range for detecting transcripts compared to microarrays