Q:

What is the correct command to produce small wedges in differential forms?

In a differential form (see, for example, Definition 10.11 in Principles of Mathematical Analysis):

there are wedge-like symbols. I found two plausible commands to produce them: \wedge and \land. In appearance, they look indistinguishable. So which one should be adopted? 

A:

As noted in a comment the two symbols are indistinguishable. 
When typing differential forms, use the command \wedge since the symbol is called the wedge product. (Similarly when you do wedge sums in topology.)
Use \land when you use the symbol as the "logical and" symbol. 
When writing notes in lattice theory I would sometimes also define \newcommand*\meet{\wedge} to give yet another name to the same symbol (and to reflect its name in the theory). 
Synonyms can help make your source code more readable. 

See also this question and its answers. 

