Different audiences
Alpha3D is built for businesses that need 3D versions of existing physical products — mostly for e-commerce, AR product previews, and catalog conversion. MagicOBJ is built for creators who generate new concepts from text or reference art.
If your workflow is 'I have a product photo and need a 3D version for my store,' Alpha3D may be the right fit. If your workflow is 'I have an idea and need a mesh to start from,' MagicOBJ is probably faster.