Sorry - we have not answered your question
So I will give it my best.
Vacuum over hydraulic systems use vacuum "pressure" from the tow vehicle to "pull" a diaphram type unit mounted on the trailer that converts this motion to hydraulic pressure by means of a piston. This unit is very similar to the vacuum boosted brakes on any vehicle on the road today.
Although I have never owned a trailer that needed this or a vehicle with a system on it - I did research this topic 2 years ago during my GN trailer purchase. I learned this:
A trailer with Vac/Hydraulic brakes cost at least $500 more, though they do stop better.
The system installed on my tow vehicle was going to cost about $800 compared to the $75 Tekonsha Electric brake controller to be used on a less expensive trailer.
Drawbacks in my opinion: Cost more, another "system" to worry about", will have to continue to have system installed on future trucks if you keep the same trailer.
Advantages: Stop better, Hydrualic brakes on trailer are more reliable, other cannot borrow your trailer as easy if they do not have vac/hyd brake controller.
In my previous post I talk about Master brake because I beleive thier Electiric over hydrualic unit can be used on a trialer with hydrualic brakes and be towed with any electric controller - thier controller is top of world in quality and performance - I could go on and on - but the best thing to do is look at the post in this forum about Master brake and then go to their website.
If i had my way I would have hydrualic disk brakes on my trailer with a Master brake elec/hyd unit and use my current Brakesmart controller - the controller I installed a few weeks ago, so I am one step toward this plan. It controls my electric brakes so well that I am not sure if I will stick to that plan.
Welcome to the TDR.