I wld choose the E550 over the A95 becuz:
1) E550 has a higher resolution than A95 ( You can see from the resolution charts at dpreview.com).
2) Faster speed of operation. The E550 is a faster camera than the A95. The E550 has faster start-up, focusing, and shot to shot speed. The Canon A-series' focusing speed can be quite slow.
3) ISO performance is better. Check the reviews from dpreview.com. The E550 can go up to ISO 800 ( only at 3MP), and it is very useable.
4) RAW mode. Some users of E550 (some of them are D-SLR users) said that if u process the RAW files using third-party software, the results can rival 8 MP prosumers. There is one very popular free RAW converter software, called s7raw. Very easy to use, with graphical user interface.
However, there's one disadvantage for the E550. The E550 has a longest shutter speed of 3 secs, compared to A95's 15 secs.