• Studies show that 20% of surfers, upon encountering a splash page, go somewhere else. They never even enter the site. So if your church erects a website to attract potential visitors, but you include a splash page, one out of five people who come across your site will not get past the splash page.
• Splash pages take longer to load than regular pages. Web users are notoriously impatient. If your page takes too long to load, they are a billion other pages they can surf to.
• If the splash page doesn't include really important information, something which justifies the wait, you risk annoying the person before he even gets to your homepage to learn about your church. Don't risk it.
• The homepage, the URL people type to get to your site--www.firstchurch.com--is the most important page on your site. Why waste it on a fancy animation?
• On the web, people's attention span is measured in seconds. Don't do anything to waste their time. That's the only thing Splash pages do--they waste your time.  
• Splash pages annoy return visitors. Even if you, incredibly, actually like someone's splash page, you will only like it once. You won't want to wait through it every time you visit the site.

Also: splash pages hurt you with search engines.
The homepage URL is the most important page to search engines. Splash pages contain almost nothing that search engines can index--no text with keywords, no links except to the homepage, no H1 titles (that's HTML-speak). All information is contained in the graphic or animation, which probably can't be indexed.

When Google indexes the page, the results won't include the church name, location, services times, or much of anything else. It's just a waste. An empty room with a nice painting adorning one wall and a door at each end.

If you want more information about splash pages....