They are both perfectly acceptable under certain circumstances yes. Though if you put them under a microscope they are pretty different. Epson's engineers desig

They are both perfectly acceptable under certain circumstances yes. Though if you put them under a microscope they are pretty different. Epson's engineers designed their inks for Epson ink delivery systems. HP engineers did the same for HP ink delivery systems. They have very interesting and subtle differences which can cause different performance. However, their compatibility is relatively high, yes. Knock off ink with less engineering on the other hand doesn't mimic HP OR Epson ink nearly as well as they mimic each other.