I wonder why the fully articulated screen slows down the auto-focus. The only difference between hinged and full articulation is the potential size of the data pipe between screen and body.
Actually, it doesn't. Those are unrelated references above - the other poster was pointing out that the Panasonic (and actually the Sony too) operate much faster with autofocus and shutter speed in live view mode, and then happened to point out that the articulation styles of the cameras differ so if you felt you needed side-to-side articulation as well as up-and-down articulation, your choices become more limited.
The Panasonic cameras do not use a mirror - they are technically not 'dslrs', but large-sensor interchangeable lens cameras. The reason they are faster than most DSLRs in focusing and shooting in Live View mode is because they work much like a traditional P&S camera in using contrast-detect autofocus without requiring a mirror to project an image to a viewfinder and flipping it out of the way to expose the sensor. Nikon, Canon, and Pentax cameras have a live view mode that uses the main sensor exposed to provide the 'live view' on the LCD, and use contrast-detect autofocus which is slower than traditional phase-detect AF...then before shooting, they take a second delay to flip the mirror down and up...making live view on those cameras more tuned to tripod work requiring manual focus accuracy, or where focus and shutter delay are non-consequential.
The Sony live view system is quite a bit faster - nearly the same as Panasonic, but with a conventional DSLR. Sony has what they call 'quick view live view', which doesn't require exposing the main sensor to provide live view - they use a second sensor...allowing the mirror to continue operating basically as it usually does, and allowing the camera's phase-detect autofocus system to operate as normal. The result is that the camera has the same AF speed whether in optical viewfinder or live view mode, and no discernible shutter delay in shooting. The Panasonic systems may be incrementally faster since they are designed from the outset as non-mirror cameras, but the Sony DSLRs are certainly the only ones capable of normal 'P&S' style live view usage. Note: some of the newest Sony models have expanded to include both their quick live view system as well as a second main sensor live view system for those needing the manual focus accuracy.
As for articulation...that's where you would have to decide which types of articulation are most important for you. On the Panasonic GH1 the screen flips out from the back of the camera 180 degrees to the left, then can rotate around 360 degrees. The Nikon D5000 screen flips 180 degrees downward, then can rotate around 360 degrees (this can be a problem when mounting to a tripod, as the LCD will be limited in movement under the camera). The Sony LCD on their A2xx and A3xx models can flip upwards 90 degrees or downwards roughly 45 degrees, but has no side to side motion. On the A5xx models, the LCD was given additional range, where it can now flip through 180 degrees up or down, but still no side to side.
Hope all that helps!
--
Justin
galleries:
http://www.pbase.com/zackiedawg 
