"Rather" appears to be a fine word choice for your intended meaning. I'm objecting to your intended meaning (as far as I can perceive it):

- [θ] and [ð] are objectively similar sounds, differing only in voicing.

- The argument is not even very good that /θ/ and /ð/ are different phonemes in English -- they contrast only in the pair of words teeth/teethe, and one of those words is fairly rare. If you, as a foreign speaker, pick the wrong one of those sounds, you have 100% odds of being correctly understood as a "guy with a foreign accent". Even if you get confused between s/z (compare "visible"), you're very likely to be understood, but with θ/ð there is literally no chance of confusion.

Thanks for the reply! I appreciate the clarification.

The variations around "th" is one of the things I remember finding particularly difficult when learning English pronounciation, so my comment came from there.