So Gary is basically talking in circles. The praetorians were, through most of their history, basically a city watch whose job was to keep the peace in the city. They virtually never saw combat, even if some members of their group had once been soldiers before they got out of shape as glorified body guards (and many doubtless hadn't). Since they were virtually never deployed in actual battle, and didn't go into the field to drill and march every day, there is basically no way they had the cohesion of an army (even in the days when a good chunk of their members had been former soldiers). A legion stationed in a volatile province was infinitely better. They had constant drills and marches to stay in shape, and keep up with battle formations and routine. They had actual experience in battle, as a single unit. A bunch of plodding city watchmen who had grown comfortable harassing civilians would be cut to pieces by real forces like these; and that's exactly what the actual history that happened shows us. When the praetorians tried to get involved in politics they were no match for real soldiers. Gary and others are living in some alternative history which didn't happen basically. It's not like history has changed matters either; the police force is no match for the army even today.
To control Rome as an emperor here are the things you needed in order of importance:
- Support of the armies
- Support of the armies
- Support of the armies
- Support of the praetorians
- Support of the Senate
- Support of the common people
- Support of the provincials
The army was far and away the most important thing. Everything else was nothing in the face of that. The praetorians were more useful than the puppet Senate though, or the people they intimidated on a daily basis.