In my case suscription models with somewhat absolute pricing were attractive because it provides a way to even out the money cost over time.
But the price was not the only thing in consideration when it came to costs.
The concerns my client had with suscription model was if the provider would still exist and provide same service in a year, or in five years for that matter. The amount of time they had to invest for the PoS (which was with inventory management) needed to be secured. They were okay with phasing in the inventory over a long period (it was a specialty store with a huge inventory) given the system didn't rely on being functional if only it knew the inventory - as long as the time investment couldn't be lost. Should the PoS provider go bankrupt or otherwise stop the service they wanted to be sure their effort time-wise wasn't worthless and could be ported somewhere else. Contracts with a minimum binding periods was okay as long as it didn't mean the time they used the system couldn't benefit them elsewhere.
Someone pointed out that the robustness wasn't a deal-breaker because you could revert to handwriting receipts. It's true that you can just do that but the point about PoS isn't just that it's slightly more effective than a calculator that can print out receipts for customers. A PoS grants valuable data. Even older cash-registers have data capabilities such as who the salesperson was and time of purchase.
If you can provide great analytic tools for the data it has gathered, that'll be a major improvement of many available PoS systems.
But store owners also care about stability very much. If the system doesn't work when there's internet shortage they won't be happy. No electricity is probably only acceptable factor when it comes to having a PoS on a computer.
If the system is slow and customers are waiting because there's unstable internet they will also be dissatisfied. Debit card processing all goes over the internet and when it's slow customers have bad experiences but at least they know it's because the internet is messing up and some ISP probably is to blame. If the cash-register is screwing it up they will blame the store.
I've worked in a store for a couple of years as a sales person so if you have more questions I'd be happy to help. I'm available through email: pierre@snowboardforbundet.com.