Among other allegations, Craig alleges Stringer alleged the ballot was rigged and only sent to selected members.
Stringer sought to have the case heard by a judge alone.
Judge Gendall in the ruling that the "general size of the present proceeding and the number of documents which would need to be considered by a jury are substantial".
He added: "There are 41 causes of action in the plaintiff's pleading. These involve 41 publications, each of which contains multiple allegations to consider. In total, as I understand it, there are nearly 200 pages of pleadings.
"I am told too that the number of documents in the common bundle will run to several thousand pages."
He said that the case was complex and consideration by a jury would require deliberation of well over a week.
"It is unreasonable to expect a jury to engage in complex matters over this length of time and thus it is said the Court needs to avoid final decisions which may prove to be unsafe."
Craig had signalled he would need to call expert witnesses on matters involving "intricate" financial detail.
Craig and Stringer were to represent themselves at trial.
"That will inevitably complicate matters if this matter is to be conducted by way of a jury trial, given the obvious lack of professional training and legal knowledge of each party," Judge Gendall said.
"I am satisfied in this case reasonably complex legal matters will arise."
Judge Gendall also said the defamation trial between Craig and Taxpayer Union executive director Jordan Williams earlier this year would have an effect on the current case because of similar issues.
In that case, the defamation claim against Craig was upheld by a jury and Craig was ordered to pay $1.27 million in damages to Williams. He has said he will appeal.
The case concentrated on Craig's relationship with McGregor and revealed intimate text messages between the two.
Gendall said in the decision on the latest case: "Finally, it is my view that, if this matter is to be the subject of a jury trial, this is likely to place significant strain on the resources, patience and effective operation of the Court, jurors, and the parties."