$ cordova emulate ios --list

で確認できます.

ちなみに私の今(2016/6/2)の環境だとこんな感じです.

    iPhone-4s, 9.2
    iPhone-5, 9.2
    iPhone-5s, 9.2
    iPhone-6, 9.2
    iPhone-6-Plus, 9.2
    iPhone-6s, 9.2
    iPhone-6s-Plus, 9.2
    iPad-2, 9.2
    iPad-Retina, 9.2
    iPad-Air, 9.2
    iPad-Air-2, 9.2
    iPad-Pro, 9.2
    Apple-TV-1080p, tvOS 9.1
    Apple-Watch-38mm, watchOS 2.1
    Apple-Watch-42mm, watchOS 2.1

よく使う環境は 5S です.

$ cordova emulate ios --target="iPhone-5s"

Reference

• iphone - Cordova: start specific iOS emulator image - Stack Overflow