We've used MCT Grammar Town, in fact am using it for the 2nd time with dd 4th gr, and then AG, after trying KISS for a while. I really liked the fact that MCT gave a sense of the big picture fairly quickly. Now, going through in detail with AG is going well for dd 8th gr. They do say in AG that there may be differences of opinion, and if the student can support their opinion then that is fine. My understanding is that there do seem to be differences of opinion about grammar, I always thought it would be much more black and white. I think it's impossible to find something absolutely perfect, and the differences in opinion allow for some practice in critical thinking.