Flat or curved--I consider flat triggers so butt-ugly I wouldn't consider buying one. But if you have a flat trigger finger, maybe it would work for you.
For triggers with a short pull--DA revolvers being shot SA, bolt action rifles, etc.-- I like a wide trigger. Love the trigger of the old Colt Gold Cup but the frame has to be modified to take it, and I don't want to add a trigger shoe to a regular 1911 trigger, so I live without. Also love the old S&W Target Trigger (.400" wide)
for single action shooting only. Hate it for DA. Some years back I happened to buy a new S&W that came with the then-new smooth .312 "Combat Trigger" and found it was the perfect compromise for both SA and DA shooting--better than the standard .265" grooved trigger for DA and MUCH better than the .400" grooved for DA, and almost as good as the .400" Target for SA. I had a couple old .400" Target triggers on hand and I promptly ground them down to the same width and shape as the .312" Combat with a Dremel and put them on my 4" M19 and 6" K-22.