I have a portable system (2.1) a Cambridge Soundworks Model 12 for many years, haven't really looked at what's available but the JBL stuff I do see mentioned regularly.
As to whether a better built/designed box would be beneficial for portable, sure, except perhaps for size and convenience. A good box, both design and construction, is important for speakers. I do wonder what a good speaker measurement (like with a Klippel) of the JBL would be like.....