Just sticking with the two you mentioned ,
both have two vacuum motors , in the storm the two motors are connected in ' parallel ' this configuration optimizes airflow ( often measured in CFM ) but that comes at the expense of suction power ( measured in waterlift )
So the Storm has about 280 CFM and about 125 " lift .
The Enforcer has its two motors connected in ' series ' which gives it high suction (lift ) but at the expense of reduced airflow (CFM )
So the Enforcer has about 240" lift and 100 CFM
Which is best ? Its best to research that your self as there is no quick and easy answer .... if you google CFM vs lift there is a thread discussing the pros and cons of both configurations .
The Storm uses a pumptec water pump rated at 800psi ... you could consider the 600 pump in the enforcer to be fairly identical
Enforcer also has other pump options .
Water heater options for the Storm are limited to an external clip on heater , where as the Enforcer has the option of either an immersion heater in the watertank bottom ... or a built in 'inline' heater (similar to the storms but built into machine ) or u could have both if u wanted . Ashbys also have external inline heaters .
Which heater is best ? an immersion heater is simple , usually cheap and reliable .
an external inline can be brought close to where your working for more consistent heat .... and a built in inline might be convenient although limited to distance from machine and could add significant weight to machine .
The storm has a gravity based waste water release system operated via remote .
Sounds high tech but its really a check valve inline and a remote power switch .
Ashbys also offer this as an option .
Ashbys also offer auto pump out , which uses a dedicated pump to release waste water as you work .
Pros and cons to both ... the autopump means you never have to switch off the machine as u work ... however they have a filter which is prone to clogging ...
The gravity based system will only empty when u switch off the machine ( via remote ) buts its less prone to failure/clogging .
Think those are the main features of both The enforcer has other options also , auto fill , chemical feed etc but u will pay hard for these extras .... these machines are at the high end of the portable market ... many would start off with lower spec machines , if u can afford them go for it , but be carefull not to blow all your money on gear only to find u have fewer customers than planned .