I am seeing the same things. My pages in the index are pretty old. Dynamic URLs have been changed to static ones a long time ago. Yahoo only shows the old dynamic URL pages. Number of pages are much less (about 1/20 of what I have in Google). Some very old pages showing up in the SERPs. It seems that the crawl was done at least 5-6 months ago. No new pages made during last the 3 to 4 months showing up. I am also seeing a lot of PDF files in the SERP for some terms.