Attorneys should favor their substantive arguments over their procedural arguments.
Procedural justice refers to the process by which the courts reach the merits of a given case. Substantive justice refers to the merits of the case.
Judges will usually give more weight to substantive justice over procedural justice, as judges like to adjudicate cases on the merits. This makes sense as the purpose of court procedure is to reach the merits of a case. Most the time judges will not penalize you for making a procedural mistake unless the other party is prejudiced, although some rules have strict compliance requirement like the statute of limitations.
Usually sanctions such as dismissal or exclusion of evidence are considered to be extreme sanctions, and judges will generally look for other remedies to cure any prejudice such as a continuance. If a judge believes the violation would substantially prejudice opposing counsel through way of surprise, and would prevent the non-violating party from being prepared at trial or create an undue delay the courts will consider exclusion or dismissal as an appropriate sanction. Courts are also likely to consider a sanction if they believe the violation was willful.
