Actually with DX12 and Explicit Multiadapter it's not a bad time to go with multiple GPUs. If AdoredTV is right, AMD is about to go all MOAR CORES with GPU clusters on stacked interposers with Navi. The groundwork for that begins now, and you have to admit the biweekly driver releases are a huge improvement.
Otherwise it's just the standard Nvidia marketing talking points, most of which is either inaccurate or no longer relevant.
Actually, considering that right now there only exists one or two Dx12 games with support for EMA, going with mGPUs is as bad as ever.
Also, even if AMD really pulls off multiGPU on interposer trick (and i tend to think that's what they are going for, considering even Greenland APU looks to be using quad die on interposer), it most probably won't work as actual multi GPU.