Looking to purchase a new point and shoot?

Personally i'd go for one of canon's g series cameras if your looking for a compact.

From dpreview.com in comparing the 550 against the s5.

Although we found the SP-550UZ frustratingly lacking in many respects there's no doubt that Olympus pulled off quite a feat squeezing a full 18x zoom range (with a true wideangle) into such a compact camera; there's really not a lot between these two in terms of detail, and the the SP-550UZ actually has marginally better corner sharpness. There's a lot more difference in color, with Canon's strong reds looking particularly vivid next to the Olympus's rather weakly warm tones.

As usual once you get to ISO 400 the differences are less obvious; noise and noise reduction are the great levelers with small sensor cameras. Both cameras manage to simultaneously suffer from noise and the unpleasant detail-destroying effect of excessive noise reduction, and it's really down to personal preference which you would call the 'winner' here. I'd personally give it, just, to Canon simply because of the better color (it retains saturation in the reds a lot better), but you wouldn't want to use either for anything too demanding.

At ISO 800 Canon's more light handed approach to noise reduction actually pays off, producing output that is very grainy (thanks to the low luminance NR), but does at least retain some detail (and looks a lot less processed than the Olympus output). Again, not a setting you'd want to use for anything serious, but for quick portraits in low light without flash - and as long as you're not intending to produce enlargements - it has its uses.

You won't go wrong with the s5 and I think you will like it a lot more than using the 550.

*Additional details*

Well xD is a proprietary format and is not as popular as SD or CF cards. Olympus and Fujifilm specifically use these xD cards. xD is slower than SD without a doubt (5MB/s vs 10-20MB/s transfer speed).

Hope this helps ... IMO i would be choosing the Canon if those were the two choices you were set on deciding between.