Many petitions against restrictions are "Dismissed as Moot." Does this mean the applicant lost? The answer is sometimes... absolutely not.
As a reminder, restrictions cannot be petitioned immediately. That means that most petitions come after a first substantive Office action at the earliest, and before appeal at the latest (due to rules on timing of such petitions). Thus, at the time of a petition, both the applicant and the examiner likely have a good idea of where the case is heading.
Strategically utilizing a petition sometimes simply sets up the case for the Examiner to take the easy way out and allow the examined claims subject to the applicant canceling withdrawn claims. For example, petitioning a restriction when the applicant has strong arguments against the rejection of examined claims can sometimes lead to the situation where the Examiner offers to allow the examined claims if the applicant will cancel the non-elected claims. In so doing, the Office of petitions will dismiss the petition as moot. However, the applicant in effects wins the allowance of pending claims and thus may be quite happy with this result (and thus this situation would not necessarily be characterized as a loss to the applicant).
However, sometimes petitions are dismissed as moot because the applicant cancels the withdrawn claims, even though there were intent on fighting the restriction with a petition. US 14/951,663 is a case on point. Here, the applicant (Xerox) was pursuing claims directed to a method for rendering gloss effect image patterns on a recording medium. The examined claims were allowed, yet the Applicant wanted to have the withdrawn (un-examined claims) examined and so petitioned. However, the petition was dismissed as moot as those claims were no longer present. So in this case, the dismissal would be characterized as a loss to the applicant.
So, strategic use of petitions can be helpful in moving a case forward, but remember that if you want to actually create leverage or win on a petition, the withdrawn claims cannot be canceled.