Official VS third-party Motormaster and Menasor! I like them both. They cost similar when I got them. They are great transformers. The official one is larger, but there are more accessories from Magic Square which makes it has more combiner modes. For build quality, neither of them is perfect. There are some loose joints for the one from Hasbro, but the combiner mode is great. For the one from Magic Square, there are some very tight parts that broke my nail twice (but it gets better after transforming a few times). But I still love them both.
Which one do you like?