For the PC for Desktop and Laptops
I like the openness of the standard PC. You can choose Windows which is easiest, most popular and is cost effective for most users. The PC's (Desk or Laptop) themselves are affordable. Linux is cheaper but there is a learning curve to get it set up and there are some limitations of available programs. iOS is stable but at a very high cost for hardware.
For Mobile for Phone and Tablets
I have opinions here, and I can't help but let my personal opinion peek out, so forgive me. There are several war camps all trying to draw their own line in the sand. Android or iOS, that is a question a new mobile user must ask themselves.
On one hand you have the openness of Android(Google) that comes at very reasonable prices and a large selection of devices. With Android you can shop wherever you want, get ebooks from anywhere on the web and even more than one app store is available. Its openness has helped it to be the most used mobile OS out there.
iOS(Apple) is a simpler device but at a very premium cost. There is no selection of devices other than the current model made for that year. I have to admit this does make the decision simpler.
Also Windows is trying to make a comeback after their failure with Windows Mobile with all new Windows 8 RT for mobile devices. Do not let the name fool you Window RT 8 does not run desktop programs, there is a proprietary Windows app store for that.
Nothing is perfect but the war goes on. Everyone has their favorite and they all get the job done within their own limitations. I really wish there was one standard though. yes, variety is good but i sure would be nice is everyone at least use the same standards. I know there are users who do not want choices or or selection to just keep things simple, it is for these users that iOS exists and thrives.
You can still have variety though, while at the same time having open standards. For example there is the PC which is open to a lot of variety, but yet you can still build a PC off the rack from standard parts of your choice.
Take also Andriod, there are many devices to choose from with many different features and hardware for use by many different types of users. Both the PC and Android use open standards but yet give their users many open choices. This is the way I believe give users choice, but yet uses standards for all to build on.