Mahogany isn't a common tonewood for Taylor tops... Usually they use spruce. You hit the nail on the head when you said it gives a warmer sound. That's about the only difference besides the appearance. Taylors are always known for their bright crisp projection - which is usually associated with spruce tops and maple sides. Martins tend to be on the opposite side of the spectrum with warmer tones - coming from mahogany sides spruce or mahogany tops.

Just depends on the tone you want... a taylor is a taylor.