As you see........this question always becomes an argument based on personal opinions. The vast majority start in this industry with portable machines, some seemingly so lacking in power in terms of pump pressure and vacuum extraction ratings.
While the theory of high power is fine and in most cases will, if used properly achieve a greater removal of soiling from carpets it's not necessary and not necessarily the best treatment for all carpets.
If, for instance, you're intention is to clean mainly commercial flooring, the best option is neither 2vac nor 3vac, but a rotary system, preferably an oscillating pad system with an encapsulation product.
On the other hand, if you intend targetting domestic work HWE is probably the best option. This is when you have to determine, who will carry out the work as the physical handling and operation of equipment is multi variable.
It's great to have the power that allows you to leave the machine in the van when it's viable, but it's not so great if you find regular work several flights up and no lifts.
As Clinton says..........there are other issues to be considered than just power.