Good question. The first obvious answer is that as of February 2020 the Smart DC DC Charger 12/12-30 is not yet available and the Buck Boost is. Here are the main functional differences between them:
This Buck Boost can go up to 50 Amps output but the Smart DC DC Charger is limited to 30 Amps output.
The Orion Smart DC DC Charger has options for a two stage charge with a settings for absorption and float voltage and a time setting for bulk, but the Buck Boost has a single output and no time out setting.
The Buck Boost has much more programming options for determining when it will turn on ( eg requiring two or more conditions to turn on) and how much current it will pass, the Orion just has an on-off switch.
You can set up the Buck Boost to work with minimal interference to the vehicle's wiring by programming it to use its vibration sensor to turn on.
Since the Orion Smart is a new product we haven't yet had the opportunity to play with it.