The Python REPL notoriously uses >>>/... like in the screenshot, αΊƒith the effect that e.g. IPython has a special paste-from-repl magic just to remove these.
Or alternatively the prompt character could start on a new line. That way you can have smaller windows fit more query per line with less space wasted on white-space.
With the "newline after prompt" scheme, you only get one extra line per query.
Which, if the query is long (e.g. longer than 20+ lines) it's not gonna make any difference anyway -- it's not like it matters if you can fit e.g. 24 or 23 lines of a 30 line query (besides, the result rows are gonna take much more vertical space, further making the measly 1 extra line issue moot).
As for for multiple small queries (and one extra line after each of those prompts), you can always scroll. And, again, the results are gonna take far more vertical space than the single extra line per prompt.
And, of course, with the full horizontal space available (and not half wasted by dots) you get to fit more characters in each line, and thus your queries will probably end up using FEWER lines.
So, not only the extra line from the "newline after prompt" is no big deal vertical-space wise, but the dot scheme wastes MORE vertical space AND renders queries unpastable.
While you are data gathering, I will half-vote the other way.
In VIM I make my whitespace visible, and just live with the consequences when I cut an paste. That said, I most of my empty spaces are still invisible, I only show tabs and trailing spaces.
You can change this to an empty space via the config file right now. In ~/.config/pgcli/config look for continuation prompt and set it to empty string.