Which BASIC pocket computers make the best calculators?

[Hollerith]

If you relax what is BASIC then I would suggest TI-Basic on the TI-86.

You can use user defined functions on the TI-86, but only 1 line functions and passing just 1 parameter.

This is achieved by making use of the eqations for Function graphing.
In a program you can define a function y99 (say)

Code:

y99=2*x^2+x
For(I,1,4)
Disp y99(I)
End

This produces the following output

Code:

 3
10
21
36

Note that defining a graph equation selects it for display so you probably want to turn this off using the FnOff command.