Some of the better professional wood machines I have seen and operated were all movable tables, they will accelerate much faster than a gantry type, they only have to move a table not the gantry motor etc. With a fixed gantry you can build that so stiff and heavy that you can reduce vibration that would only travel though the components that make make up a movable gantry. For small hobby machines movable gantry is what I would go with.
http://www.thermwood.com/twood_site/...nc_routers.htm