Heyyo, tbh the hype behind HBM and HBM2 is overrated... sure, they arguably do help quite a bit in higher resolutions to retain performance as seen in 4K UHD, but it still comes down to the performance of the GPU core itself.
Of course, there's sadly not a straight forward method of comparing as AMD and NVIDIA have yet to put out a GPU meant for gaming with HBM and GDDR variants... but if the bandwidth and speed of the memory isn't holding back the GPU core on GDDR5X? HBM2 won't really help that much... nawmnsayin?