Blazegraph has multiple backends. Their GPU compute engine vs. their classic DB engine are different ones. And yes, I doubt they use the same approach as GraphX, considering they've published how they don't (MapGraph) and GPUs require way more work. Lumping all these systems together doesn't make sense: reads aren't writes, and there's a whole world of graph computations. Benchmarks matter.

That said, I'd be skeptical of a GPU system for being great at writes, and I'd be skeptical of a non-GPU one computing better than one on GPUs.