I am a strong proponent of Lisp 1, primarily because the distinction between functions and other types of values is artificial. Functions have first class semantics in Lisp 1 and Lisp 2, but Lisp 2 makes you denote them differently but in an inconsistent manner.

Lisp 2 advocates typically make a few arguments. One is that having a separate namespace for functions makes it clearer when you are using a function vs another value. The second is that the evaluator has less work to do when examining the head of a list - it needs only look in the function environment, not the full environment.

On the first subject I must disagree - you can bind a function to a regular variable and then use that variable everywhere (except in the car of a list representing a function call), so for most positions in a set of expressions you don't really get information about whether the object being denoted is a function or not.

I suppose the second point is somewhat valid, though I suspect if you benchmarked interpreters and compilers it would barely matter. As a person who favors functional programming with a lot of combinators, I find Lisp 2 introduces a lot of pointless noise in the syntax for no reason. And I fundamentally just don't see functions as significantly different sorts of values, so I find the syntactic distinction bizarre.