I don't have any inherent problem with JJs. Their tubes are usually well made and they don't fail often. As far as high voltages go, JJ takes the cake on not blowing up - well, JJ and Gold Lion. That's about it. Chinese stuff is sometimes good but it's really variable in quality (like most things Chinese), and data sheets are not commonly available for them. Russian stuff is often not good about high voltages (the big exceptions being the Tung-Sol 6L6GC-STR which handles high voltage situations better than most 6L6s, and the Gold Lion KTs) or cathode followers.