QEMU's Assortment Of Virtual VGA/GPU Options & What To Pick For Desktop Virtualization
Longtime QEMU/virtualization developer Gerd Hoffmann has written a blog post outlining the VGA/display devices for QEMU and the recommended options. The options he covers at length include the standard VGA device, Bochs display device, VirtIO VGA, VirtIO GPU, Vhost-user VirtIO GPU, QXL VGA, QXL, Cirrua VGA, ATI VGA, and RAMFB.
The recommended solution for Linux desktop virtualization with QEMU is of course using VirtIO GPU assuming the guest OS you are running has said driver support. With VirtIO GPU support being the newest, QXL VGA is the next best assuming driver support as well otherwise Bochs. For servers where performance and other advanced features aren't necessary, the serial console obviously works for many along with the basic Bochs display option.
Those wishing to learn more about the QEMU display options can do so via Gerd's blog.