As long as the pearl is high quality & has excellent luster, the brand is secondary in importance. As for color, South Sea pearls come in the white variety or the golden variety. White can be white with rose tones, silvery tones, ect while golden can be deep golden, a butter cream color & every shade between. Tahitian pearls are naturally black, grey, silver with all sorts of tones from pistachio, aubergine, blue, silver, ect. Luster, thickness of nacre, surface smoothness are important factors in choosing pearls. The higher the quality the pearl, the better value for your money, no matter what the brand.
As for which color to choose, pick the color that flatters your skin tone.