Why not `length-cmp' which will -1 if less, 0 if equal, 1 if greater?

(defun length-cmp (seq n)
  (let* ((len (if seq (if (consp seq)
                          (let ((tlen 0))
                            (while (and seq (< tlen (1+ n)))
                              (incf tlen) (setq seq (cdr seq)))
                            tlen)
                        (length seq))
                0)))
    (if (< len n) -1 (if (> len n) 1 0))))


All other functions can be build on top of it.