Just looking for some opinions on the best trailer brake controllers. Would like something that is NOT that big black box that you bang your knee on everytime you get in the truck. I will be pulling a tandem axle boat trailer (around 5000lbs), would like it be able to brake a trailer pulling a skid-steer or two. Any recommendations would be appreciated.

Most boat trailers have surge brakes, especially if they're only 5000lb or so, so you don't need a brake controller.

Unfortunately, most brake controllers are going to be of the "black box" type but they're not all created equal. I use a Prodigy P2 and it works great, but if you want "the best" then I'd look at something like the MaxBrake controller which actually ties into your hydraulic brake system instead of using inertia to determine how much force to apply.

BrakeSmart is pretty good.

The new P2 is very smooth,even at slow speeds and ramped up.Nice feat is you can install it almost vertical and make it easy to use manually,no more cracking your knee caps.

I have a Prodigy and it is great. I swap it between 3 different trucks. They have an electric harness that plugs right in. No set-up. Works nice. Has different boost for different weights and amounts of axles. Also has a feature to slightly apply the trailer brake when backing up a hill! It is small also.

I have used a variety of types over the years (different inertia types, Jordan and now Maxbrake) and the Maxbrake is far and away the best I have ever used.

http://www.maxbrake.com/

I've had the others and the Maxbrake is the only one that I took from the old truck to this one. Proportional braking is the ONLY way to go. Rain, snow or shine. No trailer wheels locking up, no surging or jerking. There are times I've forgotten that I'm towing a trailer due to the brakes being so smooth. I never knew electric brakes could be as smooth and linear as hydraulics.
Are they more money? Yes, but every time you use it, you'll be clad you spent the few extra dollars.

No, I don't work for them. Just a VERY satisfied customer.

Ive always used the Voyager and never had any issues with em.

Always heard good things about the Prodigy too.

Got a prodigy waiting for install but honestly I havent had too many issues with my ol Kelsey Energize.

BrakeSmart or Maxbrake. Once you cough it up for one of these you won't use anything else.

If you are a heavy puller full time, the MaxBrake, Brakesmart are the way to go. For the average tow, like myself, I like the prodigy.

I have been very happy with a tekonsha prodigy but the newer P2 model looks pretty good. I tow a 28' travel trailer.

x's 2, plus the box is silver and not black

I also own the tekonsha prodigy and I have had zero issues with it and has worked great. Brakesmarts are the best but I cannot see paying four times as much for something I use 5 times a year on vacations. I am 6'5'' and my knees do not hit it unless I really spread out. I put mine to the left of the Stick Shift right above the floor console.

You can easily to find a good one on amazon. just do some searches on google and read some good reviews about it before you purchase one.
Like this one https://innovatecar.com/best-brake-controller-reviews/ or try other one to find more. Nothing to complicated.