The difference, if there is one, is that Racket provides an infix syntax as part of its definition, i. e. there is a standard notation. I''ve seen it used in the reference documentation for the -> operator when writing contracts.
Racket is a scheme, but this infix notation is unique to racket, i.e. it's not in the scheme specification. In fact, there are other proposals for infix notation for scheme, such as http://srfi.schemers.org/srfi-105/srfi-105.html
