Most local businesses we talk to are on Squarespace, and most of them are fine there. It is worth saying that clearly, because a lot of comparison articles are written by people who want to sell you the custom option. Squarespace is a good product. The question is whether you have outgrown it, and there is a fairly reliable way to tell.
Start with what Squarespace does well. The templates look professional. The editor is easy enough that an owner can update hours, add a service page or swap a photo without calling anyone. Hosting, security and updates are handled. Booking, forms and basic ecommerce are built in. For a service business whose website mostly needs to exist, look credible and let people get in touch, that is the entire job, and paying a developer to rebuild it would be money spent for no gain.
Now the limits, and the first one is the one that matters most. Mobile performance on Squarespace is capped. The platform loads its own scripts on every page whether you use them or not, and there is only so much you can do about it. You can compress images, trim third party embeds and simplify the page, and those help, but the floor is set by the platform. If most of your traffic is on phones, and for a local business it almost always is, that floor is where you live.
The second limit is structural. Squarespace works beautifully until you want something it was not designed for: a page that behaves differently for different visitors, a custom quote tool, an unusual layout, a change to how the site is crawled. At that point you are either fighting the editor with code injections or accepting that it cannot be done.
A custom build removes both limits. Built well and hosted on a modern platform, it will be faster on mobile than any template site, it will do exactly what you want, and you will own it outright. The cost is the honest part: it takes longer to build, it costs more up front, and someone has to maintain it. If the owner wants to edit the site themselves, that has to be designed in deliberately rather than assumed.
So here is the rule of thumb we use. Run your homepage through Google PageSpeed Insights on mobile. If the score is acceptable and the site does everything you need, stay on Squarespace and put the money into marketing instead. If the score is poor after you have already compressed images and removed what you can, or if there is a feature you keep wishing the site had, the platform is now the bottleneck, and a custom build is the fix rather than another round of tweaks.
That is the conversation we have with every local business before we recommend anything at Burgama. Sometimes the answer is to leave the site alone.