The DSLR is comfortable, they've been around since the days of film and have long been the number one choice for professionals and enthusiasts. So what does the DSLR bring to the table?
DSLRs pretty much come in two categories: APS-C or full frame sensors. The full frame camera is the best money can buy, and up until recently with the Sony a7 and a7R, there was no such thing as a full frame mirrorless. Despite there now being two full frame mirrorless models along with even a few compact cameras with full frame sensors, DSLRs offer the most features to go along with a full size sensor.
DSLRs also take the cake when it comes to focusing. The autofocus on a DSLR is typically faster, quieter and more intelligent than on a mirrorless. DSLRs use what is called phase detection in order to focus, which involves measuring where two light beams meet. The mirror is generally needed for this to work so phase detection is pretty much a DSLR thing. There are a few mirrorless cameras that use phase detection along with the contrast detection that's typical of mirrorless and point-and-shoot cameras, but it's limited to certain speeds and settings.
And while DSLRs may be a pain to carry around your neck all day, the larger size is typically more comfortable to grip than say the Nikon 1 J3. The more advanced mirrorless cameras tend to offer a better grip, but the grip as well as more space for physical controls typically means that DSLRs are easier to shoot with.
All DSLRs use an optical viewfinder. Many mirrorless models don't have a viewfinder at all, just the LCD screen, but some incorporate an electronic viewfinder.
The main disadvantage of shooting with a DSLR is the size. Sure, it means more room for all that tech that leads to sharp images, but they can literately be a pain in the neck to work with all day. They typically are difficult to travel with because taking your camera when it's a DSLR means packing at least one more bag, depending on how crazy you get with lenses and accessories.
While the size is the most notable disadvantage, there are a few other things to consider too, like burst speed. Every time a DSLR fires a shot, the mirrors are lifted up and down. The Canon EOS 1 DX will fire at 14 fps, but it takes quite a bit of technology to do so, part of why that camera costs nearly $6,000. Cheaper DSLRs typically only shoot at around 5 fps. The Nikon 1 J3, while it has a smaller sensor, can get you speeds of 15 fps for less than $600.
The mirrorless camera has only been on the market for a few years, but it has already impressed many consumers with their size, capability and price.
The most obvious advantage of mirrorless cameras are their size. Smaller cameras are more likely to get out of the bag more often, so a mirrorless may result in more shots than a DSLR just because they are easier to take places. A mirrorless camera and a few lenses can fit within a larger bag, making them ideal for travel.
Many mirrorless cameras don't have a viewfinder, but the ones that do use an electronic viewfinder. The picture on an optical viewfinder is what you see, while an electronic viewfinder displays what the image will look like with the current settings. If you want to shoot in black and white, for example, that's what you'll see in the EVF. The EVF also allows for focus peaking, which highlights whatever portion of the image is in focus in red when you use manual focus.
The strengths of the DSLR like the autofocus system, larger sensors and better grips could all be applied as a weakness of the smaller interchangeable lens cameras, but there's another one worth mentioning too. The battery life of a mirrorless more closely resembles a point-and-shoot than a DSLR. Mirrorless cameras are light enough to shoot pictures for the entire day comfortably, but their batteries typically won't last that long, usually 200-400 photos, depending on the model.
A few years ago, image quality would have been a weakness of mirrorless cameras, but now, it depends on the camera. A mirrorless with a sensor that's the size of a point-and-shoot won't get the same image quality as an entry-level DSLR, but the advanced mirrorless cameras have image quality that's at or near the same level as a DSLR.
Mirrorless Vs. DSLR: So which one is the winner?
DSLRs are bulky but have better autofocus and longer battery life, while mirrorless cameras travel well but don't typically offer the same autofocus speeds. So which one comes out on top? Like choosing any camera—it all depends on the photographer. Someone who travels a lot and needs a fast burst speed would likely be happier with a mirrorless, but someone who needs a lot of resolution, a long battery and a comfortable grip would be better off sticking with a traditional DSLR.
Not all cameras are created equal, however. There's a big difference between a $500 mirrorless like the Pentax Q7 and the $1,200 Olympus E-P5. If you are unsure about making the switch to mirrorless, pick up a more advanced option. The E-P5 or Olympus E-M1 are excellent, as well as the Sony a7 and the Fujifilm X line, like the X-E1.