> Tablets, like mobiles generally sufferer from planned obsolescence.
> I want my grandma to not have to relearn to yet another UI every two years.
Those two statements have little to do with each other. The current (and upcoming) version of iOS still works largely the same way as iPhone OS did 6 years a go.
Modern mobile OSes are easier to learn than desktop OSes and are less encumbered by malware. For someone who has never used a desktop computer or the Internet, starting off with a good tablet instead of a personal computer is a better choice.
> I want my grandma to not have to relearn to yet another UI every two years.
Those two statements have little to do with each other. The current (and upcoming) version of iOS still works largely the same way as iPhone OS did 6 years a go.
Modern mobile OSes are easier to learn than desktop OSes and are less encumbered by malware. For someone who has never used a desktop computer or the Internet, starting off with a good tablet instead of a personal computer is a better choice.