.png Format Vs .jpg

Rod has had me researching screen capture programs that have scrolling abilities (his favourite is Faststone). In doing this I came across a comment stating that screen shots should be saved in loss-less png format rather than the lossy jpg (jpeg). Supposedly png produces a sharper image with a somewhat smaller file size, which, I would guess, is what we all want.

My few tests saving to the png format using Prt Scr and Paint produced an equivalent or perhaps somewhat better image (keeping in mind my old eyes) but I'm not convinced regarding the file size assertion. Anyone with more experience than me care to comment?