If you are towing any of the "lightweight" A-boats with a full size SUV/Pickup then you have a "little more" margin for error but for those towing ANY A-boat with a car, mid-size SUV/pickup etc... I'd recommend brakes for sure. For ANY bass fisherman towing a fully loaded "tournament rig" be it a XB02, 03 or CERTAINLY the XB21, then I'd heartily recommend brakes and that's REGARDLESS of what you are towing it with! 99% of the time you DON'T need brakes... but that 1% of the time will be a "OH CHIT, PANIC STOP" situation where anything short of a Peterbilt will need brakes to avert disaster!!! For those towing any of the XB21 series with anything smaller than a full size SUV/Truck, I'd even recommend the option of brakes on BOTH axles!
I remember years ago after having some problems with the brakes on my XB2003 (tandem axle) I always pulled it with my Avalanche so I thought, "To heck with repairing the brakes, I'll just disconnect the whole shebang and wont need it since I'm pulling with a nearly 6k pound truck with 4 disc brakes!" Sure enough, I was rolling 50-55mph down hill, headed thru a light on our rediculous "By Pass" here in Jackson when the light turned yellow and some moron decided to lock them up in front of me! I stabbed the brakes, the ABS started burping, farting and activating and the boat proceeded to PUSH the truck thru the intersection! Only by my "Mario Andretti like" abilities and reflexes was I able to thread a needle, get around the a-hole and safely get through the intersection with straight body panels and only an enraged temper for the violator that nearly caused the accident.
(The Avalanche is on a Suburban platform and actually 500# heavier than a burb, had I been in my current crew cab pickup, I doubt it would've tracked straight. And now that I have the XB21 I wouldn't even want to think of what would've happened under that situation without brakes!!!
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Trailer brakes are kinda like a concealed weapon, nice to have and I'm always with them... but I hope to NEVER get in a situation where I have to actually call on either!