How much better are the 271 MK II when compared to the 240 MK II?   Do you think I would benefit from upgrading to a closed design?

Here's my dilemma, I am looking for a pair of over the ear headphones to become more immersed in my music. A warm noticeable low and crisp high that still maintains a solid mid, is my preference.   I do not necessarily want headphones with extended low frequencies, but that have...