A UBEC (Ultimate Battery Elimination Circuit) is basically a step-down voltage regulator. I feel that the jargon deserves a bit of explanation and history, so here goes:
In hobbyist grade remote control cars/planes/boats/etc. the electronics (receiver, speed controller, servos) need a power source. With engine powered craft, a small 6V battery pack was used to power the electronics. When electric motors became more popular, people wanted to use the large motor battery packs to power the low-power electronics. Typically, the electronic speed controller absorbed this function, and it became known as a Battery Elimination Circuit (BEC). With battery packs usually in the 9V-11V range, the electronics would probably need 5-6V to be happy.
Evidently there has been a push to use higher voltage battery packs (10V-25V), probably to take advantage of the brush-less motors. As a result, if the servos draw any appreciable current, a linear regulator would burn a lot of power. Obviously, when your flight/driving time is based on how efficiently you use your battery, a linear regulator is not what you want. Ultimate Battery Elimination Circuits are basically separate regulators (usually switch-mode) that deliver 5V-6V at hopefully high efficiency.
Now for the comparison. Your parts basically have two different end-use requirements. The Dimension Engineering product tries to match the form factor of a common linear regulator (7805). It would probably integrate better with any finished PCB you would make, and has a metal shell which hopefully shields EMI. The Hobbywing regulator is a more cost-conscious physical design, with a bit better efficiency spec. Honestly they're pretty much the same thing, so you could probably go with the cheaper one (Hobbywing).
You can use an external pass transistor with a fixed 7805 regulator, see for example page 14 of National Semiconductor's datasheet.
It's also possible to use the LM317 to build tracking regulators that can be connected together so that they share the power.
But the reason the integrated packages don't go much above 1A is the dissipation due to the product of the difference between input and output voltages times the current. Switching regulators are much better for higher currents than linears because of this thermal problem.
Best Answer
A voltage regulator produces a stable output voltage that has small variance over a range of load and input conditions.
A controller is a device that monitors and modifies the state of a dynamical system. A voltage controller could be constructed to track a signal, minimize undesired signal characteristics, or even act as a voltage regulator.