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 are right in that a switcher makes a lot more sense for your application (12V in, 5V 1.5A out) than a linear regulator. A linear would waste 7V * 1.5A = 10.5W in heat, which would be challenge to get rid of. For linear regulators, current in = current out + operating current. For switchers power in = power out / efficiency.
I haven't looked up the TI part you mention (I might have if you had supplied a link). There are two broad classes of switching regulators, those with internal switches and those that drive external switches. If this regulator is the second kind, then dissipation in the part won't be a problem since it's not handling the power directly.
If it is a fully integrated solution, then you do have to look at dissipation. You can compute this dissipation from the output power and the efficiency. The output will be 5V * 1.5A = 7.5W. If the switcher is 80% efficient, for example, then the total input power will be 7.5W / 0.8 = 9.4W. The difference between the output power and the input power is the heating power, which in this case is 1.9W. That's way better than what a linear regulator would do, but is still enough heat to require some thought and planning.
80% was just a number I picked as a example. You need to look at the datasheet carefully and get a good idea what efficiency is likely to be at your operating point. Good switcher chips have lots of graphs and other information about this.
Once you know how many Watts will be heating the chip, you look at its thermal spec to see what the temperature drop from the die to the case is. The datasheet should give you a degC per Watt value. Multiply that by the Watts dissipation, and thats how much hotter the die will be than the outside of the case. Sometimes they tell you the thermal resistance from the die to ambient air. This is usually the case when the part is not intended to be used with a heat sink. Either way, you find how many deg C hotter the die will be than anything you can cool or deal with.
Now you look at the max die temp, then subtract off the above temp drop value. If that's not at least a little above your worst case ambient air temperature, then you have a problem. If so, it gets messy. You either need a heat sink, forced air, or use a different part. Higher power switchers are usually designed for external switch elements because power transistors come in cases intended to be heat sunk. Switcher chips usually don't.
I don't want to go on speculating, so come back with numbers about your particular situation, and we can continue from there.
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Couple of $0.02 thoughts.
edit: LM25576 mentioned above is an IC around which a buck converter can be built. "Buck converter" and "step down switching converter" can be used pretty much interchangeably.