To my eye the tabs in Chrome make more sense visually too. The tabs appear connected to the document being viewed and not to the address bar like they do in Safari.
I kind of liked the Apple take on it, but I think Chrome out did them by making the tab only take up most of the vertical titlebar space. If Apple did that, I think it would have worked out better.
I really liked those Safari tabs. I guess I was in the minority though. It prepared me very nicely for Chrome tabs, though.
The top tabs do indeed make a lot more sense in a number of key aspects. But it's important to remember that the entire concept of tabs in OS X windows has long been criticized by a contingent of hardcore apple fans who argue it breaks from the one-document-per-window model. And they have a point, and it is part of why tabs in OS X are hard in general. Plus, in the safari beta they were pretty ugly and visually messy.
Fascinating how history can limit a UI designers choices...
It's more of ideology and design principle.
I loved those tabs, and I was really annoyed when they removed them in the next beta after that. I stuck with the same beta for months because of that.