Pros: Sounds fantastic, Very comfortable, Sturdy build quality, Attractive aesthetic design, Super portable, Serviceable
Cons: Doesn't isolate
This will be a very brief comparison review with the PX100, my review of which can be found here: http://www.head-fi.org/products/sennheiser-px-100-collapsible-headphones/reviews/8181
This is the most striking difference between the PX100 and PX100ii, with the latter being the far better off. The PX100 has aged noticeably, and the updated version really does look far nicer. Sennheiser have updates the aesthetics of classic without resorting to gaudy, flashy design choices. The PX100ii is sleek, modern, dark and stylish. I think it's a really great looking headphone. I especially like the little Senn logo on the arms, as well as the new cup design.
Both headphones are very well built for their respective price points, but the more expensive PX100ii improves upon the build at nearly every turn. The PX100ii is a little bit larger and bulkier in it's body, so it feels much nicer in the hands and is better re-enforced.
*Rest to come*