Which method is better depends on whether it is choosed to override or to replace the document definition. Moreover, the hevea package loads the comment package which must be present. Anyway, better control over spaces can be achieved by using the hevea boolean register or comments, see sections 5.2.3 and 5.3 . However, as an exception, the environments image and verbimage do not create scope. Relations between toimage and verbimage are similar.
Comments thus provide an alternative to loading the hevea package.
However, no environment is opened and closed and no scope is created while using comment equivalents.