Wich FA trainer should I pick?

I just got enough points to get a FA trainer. Originally I wanted to get Piers but as luck would have it I got him from a 24 hour wonder pick. Now I have to choose between him again and Sightseer. I already have two Jugglers and two Dianthas.

Who do you think will be more valuable in the future? I tend to think it will be Sightseer but I would like to hear some more thoughts.