I like both, so long as they work with the book. I also like when authors do something more with their chapter changes. For example, in Harris and Me Gary Paulsen used chapter numbers, but would also put a short, one sentence preview of what was to come in that chapter.
In Dragonflight Anne McCaffrey used poetry at breaks. Instead of chapters, the four sections were called "part (1,2,3,4)" with a part title underneath. The poetry helped break things up between parts and gave natural stopping points for the reader. The poetry also had something to do with the over all story as well. In the two following books (Dragonquest and The White Dragon), McCaffrey used chapter numbers, but also put chapter names that were location and sometimes, time stamps. These were useful as she might not have wanted to have to give exposition as to where the characters were and when they were each and every time she wanted to change the scene between chapters. As a reader, I would have found it rather annoying as well.
In The Riddled Night, Valery Leith used chapter names. The names had something to do with the upcoming chapter though. Similar to the previews Gary Paulson would do (as described above), but shorter and usually not descriptive.
Over all, I'd say that chapter numbers are the easiest. As a reader, I don't have to memorize a bunch of chapter names if I want to talk about the book. As a writer, its just easier to keep track of things while writing. If I were going to put chapter names in something I wrote, I'd also make sure it was relevant to the story. I find "just because" chapter names annoying and pointless. If you really can't make up your mind, you can always do both.
I would also agree with what Sir Icehawk said: "Write the story. Decide later." Your readers are going to be spending most of their time reading the story, not the chapter titles or numbers.
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