Strangely, considering that the two cameras are largely identical, the WB550 has slightly better overall performance than the WB500. The WB550 starts up in a little under two seconds, shuts down again in just under three seconds. It doesn't have a power-saving mode, it just switches itself off after a couple of minutes. In single-shot mode it has a shot-to-shot time of approximately 2.2 seconds, while in continuous shooting mode it can manage a consistent 1.3 seconds per shot in standard mode, or a slightly less consistent 1.5fps in the continuous high-speed mode. Annoyingly the screen remains blank when shooting in continuous mode, but at least there is an audible shutter sound so you know when the shots are taken.
The autofocus system is the same as the WB500. It is excellent, focusing quickly and accurately in almost all lighting conditions, and is particularly good in low light. The only time I found any problems was in close-up focusing close to the macro limit, but than most cameras have this problem. It usually got it right on the second try.
The WB550 has an image stabilisation system, but its exact nature is something of a puzzle. I was under the impression that it used optical image stabilisation, but Samsung's website says "...integrating the best sensor shift mechanisms of Optical Image Stabilisation..." which is of course self-contradictory. Most of the site seems to be translated from its native Korean, and as many confusing but hilarious passages in Samsung's corporate press releases attest, accurate translation into English is not one of the company's strong points. However the IS system works, it is very effective, enabling sharp hand-held shots at around 1/15th of a second even at maximum zoom.
I was quite impressed with the WB500's overall image quality, so I had high hopes for the WB550. I was not disappointed; the camera reliably produces excellent image in most lighting conditions, but there are a couple of caveats. The lens is very good, with excellent centre-area sharpness and minimal distortion at either extreme of the zoom range, but it does exhibit some chromatic aberration toward the corners of the frame.
Image noise is also quite well handled, and the camera produces good images up to 400 ISO, but there is some colour noise visible in long-exposure (over 0.5 sec) shots even at the lowest ISO setting. Image compression is also a bit more drastic than it needs to be, producing some nasty artefacts.
Although exposure metering is accurate, dynamic range is extremely limited, with even moderate shadows producing dark areas of featureless black on the final image. It does have Auto Contrast Balance, but unlike the same system on the WB500 this really only helps with highlights. It's not a crushing problem, and is common to most 12MP compacts.
The Samsung WB550 is an excellent all-rounder, and the ideal camera for holidays. Build quality, design and handling are all up to a very high standard, performance is equal to anything else on the market, and the results are very good, although it does run into problems with dynamic range and long-exposure noise. Comparing the price to its main rivals, the WB550 is a real bargain.