Image Quality – Due to the larger size of image sensors in DSLRs which allows for larger pixel sizes – DSLRs are generally able to be used at a faster ISO which will lead to faster shutter speeds and less grain (ie shoot at 1600 ISO on most DSLRs will have less noise than shooting at 1600 on a Point and Shoot). DSLRs also have built in noise-reduction when genearating JPG images which also helps cut down on noise.
Adaptability – DSLR’s ability to change lenses opens up a world of possibilities for photographers. While my point and shoot has a nice little 3x Optical Zoom (and many these days have longer ones) my DSLR can be fitted with many high quality lenses ranging from wide angle to super long focal lengths depending upon what I’m photographing (and of course my budget). Add to this a large range of other accessories (flashes, filters etc) and a DSLR can be adapted to many different situations. It should be noted that when it comes to lenses that the diversity in quality of lenses is great. Image quality is impacted greatly by the quality of the lens you use.
Speed – DSLR’s are generally pretty fast pieces of machinery when it comes to things like start up, focusing and shutter lag.
Optical Viewfinder – due to the reflex mirror DSLR’s are very much a what you see is what you get operation.
Large ISO range – this varies between cameras but generally DSLRs offer a wide array of ISO settings which lends itself to their flexibility in shooting in different conditions.
Manual Controls – while many point and shoots come with the ability to shoot in manual mode, a DSLR is designed in such a way that it is assumed that the photographer using it will want to control their own settings. While they do come with good auto modes the manual controls are generally built in in such a way that they are at the photographers finger tips as they are shooting.
Retaining Value – some argue that a DSLR will hold it’s value longer than a point and shoot. There is probably some truth in this. DSLR models do not get updated quite as often as point and shoot models (which can be updated twice a year at times). The other factor in favor of DSLRs is that the lenses you buy for them are compatible with other camera bodies if you do choose to upgrade later on (as long as you stay with your brand). This means your investment in lenses is not a waste over the years.
Depth of Field – one of the things I love about my DSLR is the versatility that it gives me in many areas, especially depth of field. I guess this is really an extension of it’s manual controls and ability to use a variety of lenses but a DSLR can give you depth of field that puts everything from forground to background in focus through to nice blurry backgrounds.
Quality Optics – I hesitate to add this point as there is a large degree of difference in quality between DSLR lenses but in general the lenses that you’ll find on a DSLR are superior to a point and shoot camera. DSLR lenses are larger (more glass can add to the quality) and many of them have many hours of time put into their manufacture (especially when you get into higher end lenses). I strongly advice DSLR buyers to buy the best quality lenses that they can afford. It it’s the difference between a high end lens on a medium range camera or a medium range lens on a high end camera I’d go for quality lenses every time as they add so much to photos.