I agree that both Perl and Python have massive interpreters, espectially as compared to the diminutive BASIC interpreter (as I mentioned earlier, I think). That's a disadvantage. But I don't know what you mean by quick runtime speed - while Perl and Python take a lot longer to start up (in the order of a second, as compared to in the order of instantaneous with BASIC), once they're going they seem faster to me. And as for ease of use, I think that Python, and Perl to a lesser extent have very well balanced learning curves. The 'hello world' program is as easy in any language, and beyond that list handling is much more intuitive in either language than in BASIC. Perhaps forcing people to indent their programs when writing Python is a little strict though.
Sadly I'm not familiar with Lua, so I admit I probably don't have the full picture when it comes to interpreted functional languages.