mavhc's such a stupid old goat. A list of RO 5 features which Select doesn't gave could also be listed and picked apart in the same pointless way. eg "PCI - don't need it, no PCI in my RiscPC" ... "HAL - don't need it, I only run RISC OS on my RiscPC" ... "USB - don't need it, I have no USB devices, or I can get a USB podule" ... down to totally stupid things like "Display Manager icon matches the configured monitor - I can draw my own icon, I only have one monitor anyway". It's futile and pointless. Nobody will need all the OS features, and many features depend on the hardware you happen to have or the machine it's run on, so stop with this bloody stupid feature-for-feature bitching.
If the features provided by Castle are most important to you, buy an Iyonix. If the features provided by ROL are important to you, buy Select.
Clearly there's a random clutch of apps that can act as some kind of substitute for Select features on RO 5, so people *do* appear to have a use for these features! Likewise, USB podules, IDE podules and new monitor icons can be added to Select machines, or you can get lots more speed by running it on a PC.
What about the features of other OS that neither RO 5 or Select has, such as preemptive multitasking, concurrent multiuser support, hardware accelerated graphics with media support, 3D graphics, software RAID, hibernation support, Bluetooth, Firewire, USB 2.0, the list goes on forever. Do we not want those in RISC OS ? Unpicking feature lists gains nothing.
If you don't give a donkey about using a modern OS, continue to use your A3000/BBC/ZX81/PDP11 whatever does it for you.