The advantage of flat bar is hydros are cheap compared to drop bars brakes on account of all those zillions of Deore & XT equipped EMTBs and MTBs zooming around. Switching to drops is hideously expensive. Tektro, always reasonably priced, don't make any for drop bars (that I can see?) so you're left looking at something like 105 or GRX, great brakes but not cheap and then the gear ratios/pull are different so new derailleur needed. Or you can check out what ever gold plated hydros SRAM sells but same pull issues.