You may well find that the increase in cutting ability is down to correct focus, currently lens are available in many focal lengths but all of them are based on imperial figures, ergo 1 inch / 1 1/2 inch / 2 inch / etc etc...
If you were told your original had a 55mm focal length then it's quite likely your supplier has mistaken or miss typed what they had said.
That said the FL of a 50.8mm (2 inch) lens is rarely if ever 2 inches, it can be as much as 2mm either way. Chinese lens are all pretty much the same actual material and standard unless you opt for Gallium Arsenides or something like RMI or II-VI infra red there is going to be a degree of *hit and miss* with quality standards.
Much the same with tubes, you can buy two from the same manufacturer and get grossly different results. Gotta love far eastern quality control