I cannot speak to which would be the best, but I have used Logitech G35's for several years, and I love them! There are definitely better ones out there, but for the price/performance provided, I have not personally found a better value.
As for whether it is worth using in games like this, I would say definitely yes! A good/decent headset will provide a much more immersive experience, that is of course once you get used to wearing a headset for several hours at a time. For me, I enjoy the additional atmospheric sounds that you can hear with a good headset, and with one that supports surround sound, you have the added advantage of directional cues which can be helpful in PVE, and are extremely helpful in PVP.
Also, if you join a group or guild that uses voice chat, the headset helps with clarity in hearing voices as well as game sounds, as well as a bit quieter environment for anyone physically near your PC... That alone, can pay for the price of a headset, depending on the reactions of those around you.