Which models are you looking at (Size, series)? The AGAs vary quite a bit among models. The Aga Pro vs. the AGA Total Control vs. the CornuFe 110 vs the CornuFe 1908 are different not just in looks, but in some key functions.

I am not sure which Aga yet, but we do like the CornuFe 110

The traditional AGAs cooker with the "always on" components are almost a lifestyle choice. Once you research how you like (or dislike) these differences, a comparison is easier.

Of the Aga DF ranges, you can see deeageaux's ranking in a similar thread.

I have a CornuFe Albertine, which I'm very pleased with thus far (a few months in). This is the single oven model, which afford more continuous interior space. The low end control is great and surprisingly even for a closed burner top. The high end power is more than sufficient, thus far, for my needs.