SSAT or ISEE for Pingry and Newark Academy (6th Grade Application)

My wife and I are Eastern Europeans and we are living in the USA for the past 12 years. Our twin boys were born here in USA and they go to public elementary school.

They are 4th graders now and we are going to apply to Pingry and Newark Academy for 6th Grade.

At home, we speak our native language and their English vocabulary isn’t as strong as it should be. Both of kids have strong Math knowledge due to my wife being a Math teacher.

With that being said, which exam will be better for them?

Thanks in advance for your help.