I can't really decide what will be best in Season 10 arenas. Ret or Holy?
From a personal standpoint, I've always played Ret in pvp and pve since TBC and have gotten at least 2k rating every season.
From a practical standpoint, Holy would allow me greater flexibility with team composition, and the major problem I've found with getting a good 3s team together on my server the past three month I've been here is the lack of any resto shamans or disc priests which are almost a must on a 3s team as ret.