Several things to consider.
1) closed versus open.
Closed phones form a virtually airtight seal around your ears which keeps music from leaking out and room noise from leaking in.
2) reference versus enhanced.
Reference phones have a flat frequency response and are intended to reproduce music with "hi-fidelity" to the source material. Enhanced phones accentuate certain frequency bands in order to appeal to the listener's specific taste. Typically, bass frequencies will be boosted and DJ's often use these.
3) comfort.
If you will be wearing them for any length of time you don't want phones that will become uncomfortable. There is a surprisingly large variation in comfort levels of various makes and models, depending on earped material, headband construction, and weight.
4) price
With headphones, it really does matter how much you spend and It takes a lot of money to reach the point of diminishing returns. Generally speaking, phones that cost between about $80 - $100 (and there are lots of them at this price) are considered "entry level", which should be adequate for most people practicing the bass and for casual listening. Many disagree, and stepping up to $150 or $200 gets you noticeably superior sound quality. Still others want even better, and spending upwards of $300 (sometimes waaay upwards) is necessary to really appreciate just how alive and vibrant music can be.
There are other factors to consider, but these are probabky the big 4. All of them are a matter of personal taste which means that taking a survey like this, while potentially useful, can only provide you with a list of other people's subjective opinions.
I could tell you that I've been almost exclusively using the Sennheiser HD280 phones about 12-15 hours per week for about 15 years for bass practice and casual listening and i really like them a lot (enough to have 3 pairs). These are entry level ($99), closed, reference phones that I find comfortable for several hours at a time. They are one of the "studio standards" at this price point, and have many satisfied users. But they also have many haters. I heard them described as producing sound that is thin and lifeless, lacks adequate bass response, are uncomfortable, and are mechanically fragile.
I once bought a pair of V Moda phones ($200) on the enthusiastic advice of several musician friends and I hated them. They had an aggressive bass boost that was overpowering and obnoxious to my ears.
Again, subjective, personal taste.
One more thing. New headphones need to have some hours of use before they "break in". Until they do, they will sound unnatural and muddy. Many users buy a new set of phones and are disappointed by the dull, lifeless sound, not realizing that they need at least a few weeks of use to settle in.
Hope this is helpful.
