I have those mentioned but as a penholder I have not play them enough to give a truthful review. So I better just give some specs and say a few words.
Donic Baum Esprit is on a class of its own. It is the cheapest and also the thickest at 6.3mm. Can't say much as I have not glue rubber on it yet.
Donic Zhou Yu Three looks promising. It is the thinnest at 5.4mm and weight 81g. I have not put rubber on it either so again not much I can say. Hopefully it has the flex I miss from OTC.
OTC is easily the best Donic I have tried so far. It does play close to a heavy Butterfly ALC. It is 184g in weight with Acuda Blue P1T on both sides. It is thin at 5.5mm, but feeling stiff all the way through. I can feel the power and high accuracy right away when I first pick it up without any need to spend time adjusting.
I bet weight difference plays a big part in shaping their characteristics. ZJK ALC, the lightest at 178g, feels kind of hollow and flex. TB ALC at 181g, feels all neutral and fast but a bit light. Viscaria at 198g feels solid and strong making high quality shots. OTC is close to Viscaria even it is much thinner and lighter. Too bad OTC is constantly sold out at most online shops so the demand must be high. But you can't go wrong with it if you are lucky to find one.
I have not play with Zhou Yu Three yet but highly recommend buying it as an OTC alternative as TTJapan is having a Christmas discount at the moment which makes it a real bargain especially for a JTTAA version.
Better act fast before it sold out too!