Why people prefer bulky SLR digital camera to small but higher megapixel and cheaper digital camera?

Differences in order of importance (popular reasons first)

Crop factor:
- up to 5 times longer lenses (real, not equivalent focal length) allows for really blurry backgrounds, this is what makes photos look professional

Chip technology and size:
- about 10 times more sensor space reduces random noise drastically
- CMOS technology reduces noise drastically once more (instead of CCD technology, which in turn supports fun things such as live view and video shooting)

...less noise leads to incredible image detail...

Lenses:
- Everything from ultra macro over fisheye up to a real telescope is possible
- only optical limitation is the content of your purse

Image format:
- RAW aims for lossless compression
- CMOS technology gets 2-3 stops more dynamic lighting from the image

Autofocus:
- much faster and more reliable because of triangular measure

Body:
- often shock-proof and water sealed
- generally more sturdy moving parts

Battery:
- quickly interchangable
- awesome run times (1500 photos and more)

Well, some people are just plain stupid and think a more expensive camera will make their terrible photography skills better...

but for me, they allow interchangable lenses and have manual features that provide us with the ability to artistically enhance the photograph.

For someone with little or no knowledge of photography, a point and shoot may be a better choice... but after you learn how to use the manual features of a DSLR, you won't want to turn back.

With the ability to use different lenses, you get to experiment more, customize - so to speak - your pictures, and try different styles. You can control the zoom and blur - or lack thereof - while still taking a high quality picture, thanks to the sensor.

Because it works so well in low light.

Canon 5D with Canon 100-400 mm f 4.5-5.6 IS L at 465 mm ISO 3,200 at 1/60 at f 5.6 (hand held)

http://farm3.static.flickr.com/2097/2419...

Same camera--at ISO 3,200 with Canon 24-70 mm f 2.8

http://farm4.static.flickr.com/3251/2420...

http://farm4.static.flickr.com/3083/2419...

Same with Canon 16-35 mm f 2.8 at 1.5 seconds at ISO 500

http://farm3.static.flickr.com/2355/2292...

Because it's the physical size of the sensor that determines the quality of the images, not the pixel count.

Bigger cameras = better pictures.

V

Much better picture quality. Better pictures at night. Interchangable lenses.

Flexibility.