50 degrees good AIO cooler idle temp?

Hey guys I have the NZXT 360 kraken aio cooler and was wondering what you guys were getting for temps. I usually idle around 40-50 degrees. My brother has the same cooler and sits around 30-40. Is the stock thermal paste poor(er) quality and does better thermal paste truly make the difference? My room is typically 60-70 degrees and I have the H6 flow case with bottom fans and a rear exhaust fan. TIA