I like readable code than compact code, that's why I prefer `when`.  I just try to follow the zen of Python even if it is not Python.

Also, what I mean by indentation is not about making code small in width.  It's about

```cl
(and
 COND
 DO-SOMETHING)
```
vs
```cl
(when
    COND
  DO-SOMETHING)
```
(though I put `when` and `COND` in the same line almost always).

I agree `and` is good for sometime when you want to write a chain of action.  For example I define `aand` or `and-let*` in big project.  But I avoid `and` when I can because `and` is more flexible (thus takes time to get the meaning of the code) than `when`.  By the same reason, I use `when` instead of `if` when there is no `else` clause.