Proprietary software: Laws often require the developers to ask for consent for this, but there's still the possibility of illegal spying, and even when given the option to consent,it's not much of a choice when they'll not let you use the software if you don't, especially in cases where proprietary software is required for work or school. On top of that, companies can make it difficult for the user to reject consent even though the option is technically allowed. For example in the UK (where I'm from), websites currently need to ask for consent before they can add tracking cookies, and rather than having a simple "decline all" option, they may have several (in some cases 30 or more) options which have to be individually declined, and they hide those options under several drop-down menus that also need to be clicked. This is done to make it as inconvinient as possible for the user to decline, in the hopes that they'll give up and just click the "accept all" option which they make easy to do. Most people in the UK will do that, especially if they're just going to a website as a one-off or rare visit. Whilst having 1 website you only briefly visited track you might not seem a big deal, there is overlap of trackers between websites, and they can accumulate data across all the "one-off" visits to create a detailed picture of the user.

Free software: It's not possible to spy, as people can see the code and see where spying is/could be taking place. People with technical expertise can make a modified version of the software that doesn't include spying and share it with others who don't want to be spied on.

Proprietary software: It could be a useful feature but it's also potentially psychologically manipulative, persuading people to spend money they would have otherwise saved. Whilst of course the user still has the freedom to ignore advertisements and suggestions, ideally they should be an opt-in feature rather than the default behaviour or worse still having no option to disable at all.

Free software: Those with technical expertise can create a modified version that doesn't include advertisements and suggestions, and share it with those don't want that either. Those who do want it can continue to use the original, unmodified version.

Proprietary software: Sometimes what it removes may be beneficial to remove, such as bugs, or it's trivial things, but it can also potentially remove siginficant things. For example if you bought a digital e-book from a proprietary store (e.g Amazon) they have the ability to remove that e-book from you. That's something that actually happened.

Free software: Any free software you obtained/purchased is given to you fully with no strings attached. You can use it however you wish and it'll likely be in a format that's compatible with a wide range of other devices and software. As free software is usually a collaborative effort, the worst someone can do is make their own copy/version inaccessible/unsupported, but in those cases you can usually just get someone elses' copy instead. You're also free to make as many personal backup copies of software as you want.

Proprietary software: In some cases it can directly do that, by taking control of the device, or in other cases it can compel the user to do so by no longer supporting features that previously worked fine, unless you install the upgrade. It's even possible that proprietary developers could intentionally share knowledge of bugs of previous versions, so that hackers will exploit it, forcing users to install the update to fix the bug. Another way forced updates can exploit users is by filling up storage and being incompatible with older devices/hardware. Given enough updates that might make a device slow and buggy, or even completely unusable. This is often the intention of proprietary companies as a way of pushing people into buying new devices sooner (and it's also one of the reasons why modern smartphones don't usually include replacable storage).

Free software: Updates are completely optional and you're free to keep using and sharing copies of previous versions, as well as versions with custom modification. If you install and update and regret it, you're also free to go back to a previous version.