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Hmm, it depends all on your preference. 4:3 covers more area or produces "larger" photos than 16:9, since the photo size of 4:3 images is 38MP versus 16:9 which is only 34MP. So if you would like to capture "more" of an object, then use 4:3. However, if you are inclined to taking photos of landscapes, then 16:9 would suit you more. Besides, there is no difference between the level of detail between 4:3 and 16:9 (since it's the same sensor and pixel density), the only difference is that 4:3 is larger/covers more area.
I almost always (99.9%) shoot 16:9 because I personally prefer that aspect ratio, it appeals more to me than the ordinary 4:3. Also, 16:9 fills up the entire screen in my L1020 as opposed to 4:3 which is cropped. However, 16:9 has a distinct distortion towards the edges of the image, so if that would bother you, then you may opt for 4:3 instead.