I think you will find that they are essentially the same, except for colors and style of trim. Thor does this duplication a lot, used to triplicate their C model lines, still duplicates more with C's than with A's.
Winnebago once duplicated almost all their model lines across Itasca and Winnebago brands. We ended up with an Itasca Spirit instead of the equivalent model in the Winnebago Minnie line because my wife preferred the interior colors in the Spirit. A factor like this might determine your choice, or maybe a dealer selling the Axis will offer a better deal than one selling the Vegas (or vice-versa).
For a long time Monaco Corp did the same with C's and A gassers, offering nearly identical models across several model lines in Holiday Rambler and Monaco brands, all built on the same lines at the Holiday Rambler plant.