There's some pluses and minuses to either approach that I can really think of
Google went their way as a reaction to not having control over the updates of Android handsets, but still wanting all their users to be able to use the latest and up to date Android applications. If you did use android back in 2-3, you will have frequently encountered issues where the OEM won't update your android version, which means you ended up stuck on oudated Google Services and google Apps. That doesn't help google. So they segmented them out. However, (i'm not 100% certain on this just yet, need mroe testing), doing this method can overall mean less compatibility between applications, Potential bugs (as they have to write messaging layers between Apps, rather than allow them to share a back end). They may require more resources, since as seperate apps, they require their own memory footprints instead of shared memory between some. Also potentially larger overall since each app would need to include more of it's own libraries, instead of shared core OS libraries, since the OS libraries themselves might not get updated on older versions.
with the iOS way. it's very tightnit and things work much smoother together (when they work). resourcing is less and things operate a lot smoother and quicker due to tie into the core and kernel. But, it means that those individual applications generally need to come bundled together as an OS update, rather than individual app updates. But since Apple does control the delivery of updates, they can get them out quickly and provide everyone access to them on day 1, but it does mean that if you need to update a single Application, you need to provide that update in the form of a full OS update, which is generally a more lengthy and involved process to install and deploy for apple (they have to QA a lot more since the update actually changes the OS).
I can't say that either one is "better", only that both have been designed around the companies focuses and limitations, and thus we have diverging paths on how each company handles it's core applications updates. at the end of the day, regardless if you're on iOS or Android, you will have up to date core apps if you keep your devices updated when necessary and this whole "segmentation" bullcrud that was talked about a decade ago is mostly irrelevant today.
