I'm not a fan of silk buttons on a tail coat. Brass buttons are much more aesthetically pleasing to me. Of course, you can always change the buttons whenever you want. Additionally, in this day and age, I really don't think it is a wise investment to own a tail coat. If you ever do need to wear one in your lifetime, you can just rent one from your local tux shop. I had to learn this the hard way. If you are going to invest in formal wear, I strongly suggest buying your own tuxedo. If you already have one, then focus on buying another, different looking tuxedo jacket.