I know that I am not Llyod, but…
You can use iFrames to do a number of things that static HTML (the second option) can’t do as easily..
Things like floating the information over your page, scroll that specific content (having scroll bars if the info doesn’t quite fit in the page area), allow the contents to scroll automatically much like a news ticker, etc…
Personally, I try not to use them if I do not have to. I do not know the SEO benefit or if all spiders can crawl them properly, so if I can get away with not using them, I don’t.
That’s my 2 cents.
kw