I have an ATPL from down under and an ATP. The checkrides are the same. The difference is the BS and red tape in getting the CAA writtens and medical completed. The written exams I had required a lot more studying than the US writtens...but I will add a lot of the material was totally useless garbage (one question was on how to tune a loop ADF antenna and another was computing an ETP with a wind change using an E6B for a C172 flight plan).Many jobs stipulate ATPL because it insinuates something along the likes of JAA (JAR) or Australian ATPL which is harder to obtain that the US ATP.
The ATP is largely worthless.