Higher bandwidth but lower capacity. The real trend is different physical architectures for different compute loads. There is a place in AI for bulk albeit slower memory such as extremely large date sets that want to run internally on a discreet card without involving pci lanes.
This is also not true. You can transfer from main memory to cards plenty fast enough that it is not a bottleneck. Consumer GPU's don't even use pcie5 yet, which doubles the bandwidth of 4. Professional datacenter cards don't use pcie AT ALL, but they do put a huge amount of RAM on the package with the GPUs.
