I'll say that the Monogram kit has a better fit/finish thing going for it. There is not as much clean up to do to it either. It's a rather simple (read: plain) model that a person would probably need to add quite a bit to it if you're a details freak but overall, it's a great model. The only other thing I could say about the Monogram kit is that it looks great when sitting but itself but (to me anyway) it looks like it's too large. I'd say it scales out closer to a 1/22 or something. I haven't actually measured it but when it's sitting next to Monogram's '58 Thunderbird, it looks too big. It's proportionately appealing to the eye in itself though.
In a nutshell, I would go with Monogram's kit over AMT's in my opinion.