Uncompressed is the best quality - e.g. RAW. But, that takes up quite a bit of space. Compression is acceptable to most amateurs and non-pros (even the better cameras can shoot with compression and still suit the pros).
It doesn't matter if 99% of the time your pics are web or 4x6 - I can tell the difference between 2vs4vs6vs8vs12 MP cameras on a 4x6 picture. Regardless, taking shots at best quality compression will give you flexibility in the case you might need say, an 8x11" print of something you shot a while ago.
I'm sorry about my outlandish behavior - there's too much blood in my alcohol system.