Thank you so much all. I have started the journey with my workplace. For someone who would read this thread later, it turned out that at the 3 year mark 2 things are additionally needed in 186 DE in my case.
1. A positive skills assessment (for Management Consultants, it is from VETASSES), which is not needed for 186 TRT. This involves costs, as VETASSES charges around 1,000 for the assessment.
2. A letter from the sponsoring organization justifying the genuine need for the role in their organogram for them to function properly. This is not needed for 186 TRT as it was already justified at the 482/457 visa stage.
The additional requirement of these 2 documents makes 186 DE a slightly lengthier process, and 186 TRT is more streamlined with the sponsoring organization. The applicant is not needed to be working under a 457 or a 482 visa for 3 years for the organization in case of DE, so in my case it could have been faster. But, given current timeline I will be eligible for 186 TRT anyway by the time we are ready to lodge, so may be we will be pursuing TRT.