Prepared statements (PREPARE and JDBC) are a lot slower than "normal" ones.

We are seeing a quite heavy slow down when using prepared statements in 10.1.

I haven't done some thorough testing, to be honest, but what we are having is a
select from a view (complexity of it should not matter in my opinion), something
like this:

prepare TEST (text, int) select * from OUR_VIEW where COLUMNA = $1 and
COLUMNB = $2;

-- Actual test code follows.

-- Takes ~2 seconds.
select * from OUR_VIEW where COLUMNA = 'N' and COLUMNB = 35;

-- Takes ~10 seconds.
execute TEST ('N', 35);

Both return the same amount of rows, order of execution does not matter, these
times are reproducible. If the same select statement is executed through JDBC it
takes roughly 6 seconds (execution time only, no data fetched at that point).
I'm a little bit at a loss here. Is such a slow down "expected", did we simply
miss that prepared statements are slower? Or is there something else going on
that we are simply not aware of?