Most good Android tablets, are atleast as much as the iPad when considering cost, however you could then posibly get away with using off the rack MSR or barcode readers, provided, that the Android device features USB.
The bonus of using iOS, is predictable behavior, sleek design, better custom accesories (iPad msr) , percieved value of the customer, but also the ability to get a replacement device, with ease.
If you go with Acer X, you have no idea of availabilty 2-3 months later, let alone a year or two.
I think I would go trough the App Store, and just use som kind of authentication, as that would be easier for some clients, and would provide better visibility of the app and the company.
However, if you would rather sidestep the regular appstore, Apple provides something called the Volume Purchasing program. With that, it is possible to provide apps directly to devices, either for free or a paid solution.
The bonus of using iOS, is predictable behavior, sleek design, better custom accesories (iPad msr) , percieved value of the customer, but also the ability to get a replacement device, with ease.
If you go with Acer X, you have no idea of availabilty 2-3 months later, let alone a year or two.