When it comes to stability of hardware and software Ericsson is the best but it costs too much. NSN and Huawei are almost similar when it comes to hardware failure rates NSN is only slightly better but thats why Huawei due to low cost is kicking out NSN from many operators. ALU is ok but very similar to Huawei. ZTE and Huawei are very similar in quality but Huawei is still better. Motorola hardware is also very good and stable but its almost out now. So overall if you consider quality not cost then its Ericsson but if you want ok quality with low cost then Huawei and ZTE are ok to use.