I don’t know about Ateres, but I can tell you about Seminar.
It’s really a good place. Good Frum BY girls. They are very caring. Have amazing teachers and amazing classes. They have the best ymei iyun!! For real!!
Also- the dorm is very nice and comfortable. All the rooms are air conditioned!! And the BEST food!! A real good American cook!!!
I heard they have changed a lot for this coming year, stronger BY type, and they’re very on top of the tznius. I heard they have a new program- something about the next step- preapring the girls for the next step in life- how to find a job that’s your type, preparing for job interviews, etc..
Let me know if you have questions! I love it so much and would love to help you have that experience too!!