I just bought some rowaphos at a pretty good price. Is it actually the best media for removing phospates???

Most all the granular ferric oxide (GFO) or granular ferric hydroxide (GFH) medias are very similar in performance. There is a variation in things like grain sizes and some are pelletized so some may last longer than others as far as physically breaking down or clumping but most come from the same initial sources. Bayer Chemical is probably the largest manufacturer of ferric oxide media in the world and ultimately supplies much of what you buy no matter the vendor.