The sensor size of the camera decides how much detail of from the captured image gets stored and also how much image gets cropped. With smaller sensor sizes the ‘crop factor’ becomes considerably big and less amount of data details get stored making the image look pixelated.
However, nowadays a new breed of point-and-shoots are emerging- the mirrorless cameras with interchangeable lenses such as the Sony Alpha series or the Panasonic Lumix series. The automatic functioning of a point and shoot makes it easy to learn. Quiet operation and inexpensive price range make it a good entry level buy.
DSLR expands to Digital, Single, Lens, Reflex i.e. cameras with live optical viewing. There is a mirror that allows you to see the image you’re about to shoot through the viewfinder. The most compelling advantage of a DSLR is the picture quality, which is a result of the large sensor size and the fact that it can be used at faster ISOs, leading to less shake.
DSLRs come with a range of lenses, which is important in architectural photography. You may often want to switch between shooting a wide-scape of the London Bridge (using wide-angle lens), and a close-up of its intricate metal patterns (using telephoto lens). A DSLR thus fosters flexibility. And lastly, every photography input can be controlled in DSLR photography, right from the shutter speed to aperture size to the ISO setting, allowing you to compose the shot the way you want it, and not how the camera envisions it.