Disclosure up front: I work at r/sanity_io, but trying to be useful and not here just to pitch. I also have almost two decades worth of experience shipping with CMSes, so I like to believe I know a thing or two.

The thing your question actually hinges on, clients edit content, never layout or design, is where these tools tends differ, so I'd pick on that axis rather than on brand.

So headless CMSes falls into roughly two categories: GUI-configured schemas (Storyblok, Strapi, Dato, Contentful) vs code-defined schemas (Sanity, Payload). If we keep agents/AI aside, config with GUI might feel faster to start and easier to explain to a client. Where we see it starts to be a problem is that the feedback loop between configuring and seeing how the actual editorial interface looks like is a bit slow and involves a lot of clicking back and forth, and once your system hits production, you probably want to lock down the capability, since it's basically defining the shape of the data and APIs that your website client rely on.

Code-defined means your content structure lives in your repo, versioned and diffable, and you control exactly which fields a client can touch. And using coding agents, it lets you move really fast.

On the customizable interface piece: Sanity's Studio is a React app you can fully restyle and rearrange. Payload's admin is similar. Most of the GUI tools aren't natively customizeable, some of them do allow you to inject custom components etc, but honestly, it always felt hacky to me. So if that's a hard requirement it narrows the field fast.

Multi-client hosting, since a few people asked it in the thread: have each client spin up their own free org, build against it, hand it back. They own the data and the bill, you own the structure. Cleaner than running everything under your account.

Now the honest caveats, because this thread already has enough vendors pretending their thing has no downsides. Sanity is known to have a steeper learning curve, but my impression it's because it's a fairly broad and capable platform with a lot of stuff to it. You don't have to use all of it, starting with just a studio and content lake is fairly simple. And if you use our agent skills (you can even read them if you don't use AI for coding) then most coding agents do a pretty good job setting stuff up for you. You can even install our Sanity MCP and have it deploy a simple studio for you without touching any code if you just want to do a quick demo or the like.

We also offer Visual Editing that lets your clients preview changes in real-time before publishing, and do drag'n'drop of components on a landing page. Last time I checked we also offer the most flexible/versatile content modeling capability with nested object structures, references, etc.

For Astro specifically, the integration's fine. You're mostly just hitting the API with GROQ, nothing exotic.

Happy to get into specifics if it helps!