Unless you plan to run graphics intensive applications in the VM(s) such as CAD or video editing/playback, you may not notice much difference in graphics performance.
With an Intel HD 530 with Workstation 12.5.x, it can still support DX10 in Windows VMs and OpenGL 3.3 in Linux VMs.
With a discrete graphics card, obviously the processing power even of an entry level Nvidia GTX 1030 would outperform that of the UHD630. Having a discrete graphics card also frees up the Intel CPU and probably generate lesser heat for the Intel CPU.
Given the current cryptocurrency mining craze, graphic cards such as GTX1060, GTX1070 are in short supply (or if you find them their price is at 50-100% above MSRP) and you might be only get your hands on GTX1030/1050/1050Ti or high end 1080/1080Ti. You would likely only find the same situation on AMD graphic cards. The middle-tier graphics card are in short supply leaving only the entry level or the expensive high end graphics card readily available at near MSRP.
