The HP 48/49/50 series is more of a competitor to the TI89.
The HP50G is a fairly extensive ARM based computer not a calculator. It is ridiculously powerful. It is discontinued now in favour of something pretty and shiny but vastly inferior.
If you're into stockpiling them, it wouldn't hurt to get a TI-89/92+/voyage200 while at it, and see the best the other relevant calculator maker has to offer ;)
I've had hp50g for a long time, got a ti-89 recently and became enlightened.
The HP50G is a fairly extensive ARM based computer not a calculator. It is ridiculously powerful. It is discontinued now in favour of something pretty and shiny but vastly inferior.