There are many variations on the VMC and HMC with manufacturers trying to gain an edge in cost vs. utility. For example,
here's a Mazak that has a moving column for the Y-axis. Mighty Viper and Mori Seiki have also made machines where the spindle moves in two axes.
The HMC's principal advantages are that the chips fall out of the cut zone more easily than a VMC which allows greater material removal rates and that all Z axis moves are not fighting gravity so the spindle can move at very high rates compared to a VMC with a counterweighted head. In addition, HMCs have the spindle/motor as an integral unit instead of having a separate motor driving the spindle via a belt/gearbox which means less mass to accel/decel for tool changes and rigid tapping.
On VMCs, the designer also has to consider how far out the spindle is hanging from the column. The more Y-axis travel, the further from the column the spindle must be to allow the table to move back far enough. HMCs don't have this problem to cope with.
Bridge gantry type machines are great for high speed and positional accuracy. But as noted, they lack the rigidity needed for heavier cutting. Thus, they work well as routers where there is little tool pressure and as circuit board drilling machines. They do poorly at precision side cutting because they flex too much.