Advantage of Scramjet vs X-43?

You question is redundant and contradictory... The X43 uses a scramjet engine, there is no difference.

I am wondering why we are not having any progress with it. Apparently the structure of the airplane can't take the forces involved, and we have to wait for that technology to improve. Do you have anything helpful to add?

The physical and thermal forces at these speeds are incredibly difficult to engineer for, it's at the limit of materials to deal with in a repeatable manner. The temperatures are so high ALL material exhibit some form of reducing action over time.

This is along the same lines of the Space Shuttle. It was supposedly a re-usable space craft, except that due to the stresses it underwent during take off and landing, every square inch of the entire vehicle needed to be rebuilt before it could fly again.

Material sciences are being advanced at a rapid pace right now. The X43 was mostly just a test bed for the engine itself, and data collection for the forces involved on the airframe

It has currently lost funding and is on indefinite hold. I doubt it will ever be progressed much further than it currently is, the information they've collected from it will more than likely be used on future prototypes of different design as they realize how best to combat the issues involved.

Thanks for your information. Hopefully we will see materials and designs that will allow it to be used.