Do (cheap) SD modules support file I/O?

I noticed there are cheap SD modules and complete SD shields. I assume the last are used for a 'final' product and not for bread-boarding (?)

However, I was wondering, is there also a difference in functionality or more important, support for e.g. the sd library (thus having file I/O in addition to SPI interface)?

Same functions. I'd prefer the external module. A shield often block access to other connections. Lower $ is a + too