database vs text files

Pardon the "lazy question"... I could probably just as easily look this up...

I'm creating a php script which will hopefully get a lot of traffic, and which will collect lots of data from users. I expect that writing directly to text files will be less work for the server than writing to a database, but I thought I'd ask. Is this correct?

(The files won't need to be read, just appended.)

Thanks