This may seem like an odd comparison but the truth of the matter is that both of these headphones are in the same street price range and they are both semi-open headphones. The Bose Triports may not seem like it from the picture, but that little mesh screen allows the headphones to be open to the outside world. Both of these headphones also reduce outside noise slightly, and have very good qualities in terms of sound reproduction.
The Bose Around-Ear headphones had a very comfortable fit; I could listen to them for hours without noticing them, but the Sennheiser fit was even better. The HD595s also came with a nifty table/shelf mount so you could hang the headphones up after. The construction quality of both appeared to be about the same, but from the experience of some of my friends, the Triports started falling apart so that they were loose within a few years and would squeak and turn in directions not designed to turn.
Now the important part: Sound quality. The Bose headphones had a very warm response. The frequency response graph isn't flat however and the bass is raised above flat levels. This creates a warm ambience, and if one of the holes (one of the ports) are covered, the response is reverse. A very bright and tinny response is seen. This is how the HD595s are but much more flat– until you get into the 8,000+ hz range. At that point, the response graph goes crazy! It appears that the drivers in these headphones can't reproduce some frequencies well at all (over -10db) but others are overproduced (+5db). The Bose headphones do this too, but not quite as badly.
Obviously the audience of these headphones are different, so you should choose based upon which type of music you listen to more. For bass heavy music, such as Rap, Hip Hop, R&B, and some Rock, the Triports will suit you better, while for Classical, Acoustic rock, and anything you need to monitor precisely, the HD595s should be the cans you choose. These are both great headphones, but I think the HD595s are better– not that all music sounsd best with them, but you can tell when you're hearing well made music, and poorly made music. If you have to, use an equalizer. You can hear poorly mastered tracks much easier with the HD595 so don't plan to use them with Satellite radio or 64kbps (maybe even 128kbps) MP3s. I'm going to try to get some HD650's to compare the HD595's to for monitoring music. Watch out for our next review
Bose Triport – 7.5/10
Sennheiser HD595 – 8.5/10
As always, shop wisely because the street prices on these (and most other) headphones are much lower than from the manufacturer.