That second one, from a basic analysis... it isn't really much different to a helicopter in its principle, given the size and spacing of the outer turbine blades. An obvious concern given the similarities to a helicopter is how well can something with a rotor the same size and an even larger jet engine stay in the air if it has a smaller fuel tank?

As for the design they actually constructed, it seems like it would be a lot more feasible with modern technology. It's not clear to me that there's any actual advantage to building a flying saucer though, other than novelty.