[bitwize]

Oh God, Newlisp. Don't worry about that. Start with Common Lisp. It's probably the most Pythonic in that it's built for building real applications in. SBCL is the open source implementation everyone seems to favor.

Runners up are Racket and Guile.

The "Lisps in Python" (like Hy and Hissp) are nice, but they're not very Lispy. More like Python with sexpr syntax. For Lisp on a Python runtime, I recommend Calysto Scheme for messing around: https://github.com/Calysto/calysto_scheme

It's slow, but it's full Scheme.

[gilch]

What, specifically, is lacking?

[bitwize]

From Hy and Hissp? Nothing really, but if you want to learn Lisp, it's best to learn Lisp and not Python in a Lisp skinsuit. The idioms between regular Lisp and Lisp-flavored Python are different.