He should choose saki. Shes also his slave master but atleast she is more open than suzuka and can talk about her problems to him or atleast give hints. Also she is his childhood friend and first love.
You never forget first love.
For me now its like
yamato felt saki rejected him and traveled to tokyo he meet suzuka there and fell in love uncounciously (<- hard word dont have time to look into dictionary^^) to forget about saki. So we could say that he loved saki more :P.
Nah nah dunno but yes it was said and i even said it that toudai is 100% guaranted to get in while in soujodai he need to pass some selection which the school make.