I have a Nikon D7000 and I see there are a couple remote release options from Nikon: the (wired) MC-DC2 and the (wireless) ML-L3 which is also about 40% cheaper than the wired remote.
Are there any good reasons one would choose the wired remote instead of the wireless, especially given the price difference?
Infrared triggers can lose their minds when in the presence of sunlight or a strong IR source. The sun puts out SO much IR the receiver can't see the signal unless its window is in shade or very close to the transmitter. They do work really well indoors or at night though, and cost less than the radio triggers.
And, just as a FYI, a toilet-paper tube taped over the window can help the receiver pick up the transmitter's IR burst when there is a lot of IR noise as it helps the receiver's "eye" see the right IR source.
For that matter though, even PocketWizards can get confused when in the presence of lots of radio noise or certain transmitters. I had a shoot where I had receivers on both sides of me lock-up multiple times. I'd used them in the same location several times before with no problems, and the only difference was the announcer was using a wireless microphone. I'd have loved to have wired up sync lines and turned off the wireless that night.
Disclaimer: I have not tried a D7000 yet, so I'm answering in general terms.
The only downside I know of is for using Bulb mode on some cameras.
With a cable release: You press the remote button, hold it down and then let go when done. Some remotes have an option to keep the button locked down, but you have to release it at the end of the exposure.
With a wireless release: The principle is the same except that you need to keep aiming at the camera's IR receiver. Otherwise, the camera may interpret the lack of IR signal as closing the shutter. If anything passes between the remote and the IR receiver, it may also happen.
The exact behavior depends on the exact camera. The idea is that you click once to open the shutter and click again to close it.
On some, there is an option to control the behavior. I know both Pentax K-5 and K-7 (excluding original F/W) have that option.
I have a wireless RF remote for my camera and now that I have wireless I would not do wired. The main reason is that there is less chance of tripping over the cable or having to worry about being tangled in it. Or if you are doing pictures with you in them you do not have to worry about hiding the cable.
Having said that I would recommend RF (radio frequency) over infrared. The biggest reason is that you do not need to have line of sight to the camera using RF. In addition from previous experience not everything IR works outdoors in the sunlight.
I use a Phottix Plato http://www.phottix.com/en/wireless-remotes/phottix-plato.html as my wireless remote. It has worked very well for me. I will be the first to admit that I do not have much experience with photographic releases but it has met all of my needs and is a lower price than some of the manufacturer's units.
For these two specific units ...
Wireless ML-L3 - good for distance and convenience (for example it's easier to be in the shot yourself), but bad as needs line of sight and is unreliable in strong sunlight.
Wired MC-DC2 - good for the fact that you can lock it with the camera on bulb for exposures longer than 30 seconds, but bad as can only be used as far as its cord of 1 meter.
Both can be used to fire the shutter without touching the camera so reducing camera shake, but beyond that they have their own specific purposes.
Rather than ask which is good from these two you would be better to ask why you want a remote shutter and what you will be using it for, then find one to fulfill that need. Personally I use two remotes, one infrared which has the capabilities of firing when the beam is broken and hence can be used to capture moving objects like animals. My second one is off of eBay and is a wired remote that has intervalometer capabilities, for example it can capture one frame every 30 seconds for 900 frames, cost was under $30.
The main disadvantage between IR remotes and wired releases is that IR isn't that reliable outside in bright sunlight. It works much better at night or indoors, but outside, the sunlight can overpower the IR signal and drastically reduce range and/or reliability.
IR also requires line of sight between the IR remote sensor on the camera and the remote itself (think: tv remote). And most dSLRs have this IR sensor on the front of the camera in the assumption that you will be using the remote to make selfies (or group shots with yourself in them)--not that you will be using the IR remote from behind the camera. If you plan on using the remote for long exposure or night sky shooting, and you're going to be working from behind the camera on a tripod, it can be an interesting exercise in contortions of the wrist to get that remote pointed at the sensor.
RF (radio) remotes can typically remove the line-of-sight and range restrictions and work well in daylight, but instead of having to remember a single unit, you now have to remember two: the remote transmitter, and the receiver unit that plugs into your shutter release port. And both of them will require batteries. If you are considering an RF shutter release, realize, too, that most flash radio triggers can double as shutter remotes, so if you were planning on "going Strobist", you may be able to make your triggers do double-duty.
Wired releases may or may not require batteries, but you still have to remember to bring it along to use it, just like a wireless remote. But many wired releases can have additional features you will not find on wireless remotes: the ability to lock down the shutter button for bulb mode, intervalometers, timers, etc. But, of course, they're wired, so your ability to work the camera remotely is more limited.
Basically, these are two different tools, not replacements for each other, and many photographers happily have both in the bag.
I have both a wired and wireless remote for my Pentax K-7. Aside from technical considerations mentioned in other answers, the Pentax wireless remote is very tiny and easy to misplace in the camera bag, while the wired remote is bigger and easier to find. With Nikon or other brands, your mileage may vary.
Wireless:
Wired:
The IR most remotes use is actually visible to many digital cameras - try pointing an IR remote (any IR remote) straight into the lens of a digital camera set to live view. While irrelevant in a single-camera, daylight, simple-trigger scenario, this could interfere with high-ISO bulb shots, or when multiple cameras are in use in a setting at one time....
If abovementioned experiment works, the "IR filter" in the camera won't help, IR remotes typically use an IR band very near visible red light (some remotes are actually faintly visible to some people!).
