I have a text driven site and I have dynamic pages that I need to optimize to get into the top 10 in most of them. I was wondering if there's significant advantage of CSS over tables and if I should take that fight to my IT department.
Yes, you should, only because that's how the web progressive and that's how we roll these days. I don't think there's an SEO benefit but I think it's important to follow and maintain some of those standards. If your website is using the font tag, that's bad becasue it's deprecated. Can you make an argument that you can rank way better? Not really. I wish that search engines did reward valid code but they don't.
Way back, if you had a lot of elements inside of your table, the page wouldn't render until everything loaded. It's about user experience too.
The bottom line is that it's not going to affect your SEO. If it's a big deal to revamp your site, don't do it.