Ditch Your Point and Shoot: Five Reasons You Need an SLR
Like David vs. Goliath, only if David had gotten thoroughly whupped

These days it seems like everybody has a camera. A teeny-tiny inexpensive camera. You'll find them built into cell and smart phones. You'll find them in notebooks, tablets, and personal music players. And the dedicated compact camera market has never had such selection. One look at prominent online retailers reveals, literally, thousands of point and shoot models – some that are so slim and so lightweight they'll virtually disappear in your pocket.
So, if you have a camera integrated into your personal device or if you can get a perfectly decent purpose-built compact model for less than three hundred bucks (which you can), why on earth would you even consider dropping five, ten, even twenty times that much money on a full-blown SLR that's not only several times larger and several times heavier but also sucks up even more bucks when you start buying good lenses for it?
Because with your iPhone or your CyberShot or your PowerShot, it's much, much harder or downright impossible to get a pic like this:

Or this:

Or this:

Okay, so you won't get results like that without a little judicious post-processing either, but the point is that only with an SLR will you have the distance, the speed, the perspective, the depth of field (more on that shortly), the low-light performance, the quality of image capture, and the weatherproofing you need to ensure you can catch virtually any subject at any time.
While many photographers jump into the hobby with a compact point and shoot and stay with that format forever, others inevitably feel frustrated over its limitations and make the ultimate leap to the big leagues. Yes, there are numerous concessions to be made, but for the truly addicted, and the truly passionate, those concessions are worth it.
So…what exactly do you get with an SLR that you don't with a point and shoot? Let us count the ways…
The Sensor
At the heart of every digital camera ever made is a device called a sensor. A silicon chip housing millions of miniature pixels, the sensor is the device upon which the image is captured. The shutter button is depressed, et voila, the sensor captures the light that's allowed in. Like the cubic inches of a muscle car's engine or the speed of a computer's CPU or the length of a man's…er, thumb, the camera sensor has long been a bragging point amongst more macho types. "Dude, how many megapixels is your camera?"
Yet it's not just the number of megapixels, but the physical size of the sensor (and therefore the pixels on that sensor) that really means something. And because the sensor in an SLR is several times that of a compact camera, it is thusly that much better at capturing light – an especially valuable attribute when a photographer is working in less than ideal conditions. Ultimately, SLRs take better, cleaner pictures, particularly in shadowy situations, than their compact brethren. The following shot was taken when the lighting was very poor indeed:

Ah, but that's not the end of the sensor issue. Some SLRs have bigger, better sensors than others. For example, "full frame" SLRs such as the Canon EOS 5D Mark II have bigger sensors than those you'll see in "crop" SLRs such as the Canon EOS 7D or the Canon EOS 1D series. But these are topics for another time.
The key thing to remember is that SLRs = bigger sensors = bigger pixels = better pictures, better performance, and less visible "noise." And crisper enlargements too.
The Viewfinder
There's clearly something to be said for lining up your images through the LCD screen of a compact "point and shoot" camera versus pressing your eye to the optical viewfinder of an SLR. For starters, using an LCD means you don't have to scrunch a whole camera up to your face – a real annoyance for those who treat their camera as a fashion accessory. Perhaps more importantly, many people find it more comfortable composing their photos – figuring out the artful side of their images – by looking at a screen held at a distance.
There are practical benefits too. If, for instance, you find yourself shooting over the top of a crowd of people, holding your camera above your head, there's no way a viewfinder will work for you. In cases like this, an LCD is the only way to go.
But the optical viewfinder of an SLR has several appealing perks, the most obvious of which is focusing. Simply, it's easier to judge when your subject is clear and pinpoint sharp when you're peering directly at a particular scene rather than a digital representation of it. And with an SLR, that's exactly what you're doing.

Moreover, unlike the LCD of a compact camera – or even the electronic viewfinder found in some compact models – an SLR's optical viewfinder conveys precisely what your camera sees. It isn't marginally above or to the side, and it won't wash out in bright sunlight. And, because it isn't electronic, it won't deplete your batteries.
Using a viewfinder also means you'll better stabilize your camera while you shoot. Think of it this way – a camera supported by two hands and a face is likely to be less shaky than a camera supported at arm's length. The less vibration, the sharper your photo.
One other thing. Most recent vintage SLRs now offer something called "Live View," a feature that for the most part mimics the LCD of a point and shoot. It isn't quite as convenient because there's a slight delay as Live View engages (the SLR mirror physically flips out of the way), but SLRs with Live View essentially offer the best of both worlds.