The difference being, that you can go and launch your payload on several pure rocket launchers today but, your payload will have evaporated before this "spaceplane" ever exists.
Like the Stirling engine, the efficiencies claimed for this regenerative heat cycle and cryogenic cooled, air-compressing, condensing and breathing/pure LOX/LH2 variable cycle rocket engine do not stack-up. The theoretical efficiency factors do not translate into the weight-limited reality that would be needed to make it competitive in orbital operation. The plant required to achieve the theoretical efficiencies is worthy of a ground based Nuclear powerstation.
Somehow, it is proposed that the efficiency of wing-borne lift within the atmosphere, burning Hydrogen fuel with a small amount of ingested air, cooled and compressed by energy from carrying extra liquid Hydrogen fuel that also provides cryogenic cooling of the air through bulky heat exchangers, will provide some earth shattering increase in efficiency. Of course, this also ignores the extra weight of the wing-borne structure and it's aerodynamic controls, the extra weight of the complex engines that have to be lifted all through the flight and reentry, the extra Hydrogen fuel/coolant to operate the air-breathing rocket, the take-off and landing apparatus, the extra propellant burn during the slow ascent and, the deadweight of the additional propellants that are needed to accelerate the relatively slow spaceplane to orbit after the interface between wing-borne/air breathing and the pure rocket/ballistic operation above the atmosphere, compared to a non wing-borne multi stage pure rocket.
There is also the question about the construction of a large spaceplane that is intended to be re-used, the weight of the structure to survive reentry, heating, flight loads and landing. Oh yes, landing. On a runway, like the takeoff?
However, the benefit of wing-borne lifting a ballistic rocket to some altitude and speed for launch to orbit (like the Pegasus launch system) does have some performance advantages but, of course, there are the practicalities of size.
Now, there are certainly interesting possibilities for high altitude atmospheric flight but, I reckon that the the multi stage rocket has got orbital lifting well and truly wrapped up for generations.
OAP