i think ICSE board is more of mugging up and learning too much information, most of which does not even come in the exams, and kids have to still memorize by force. i have seen my SIL's son who is in ICSE board doing this since class I and he is now in VIIIth. on the other hand, i feel the way of teaching in international boards is very practical, because there is a lot of real life approach to things that children can learn better, because they don't have to memorize it, but learn through real nad everyday concepts.
we grew up studying in CBSE while my kids tried out both ICSE as well as the international board. i did find a difference in the method of teaching. and i felt that the concepts are way clear in the way they are taught in the international boards.