Why are multiple engines different?

Emily wrote:
Even with a multi- rating it is not easy to find a twin that you
can rent on your own.

Really? I've never had a problem.

So far, the one I am renting (a Duchess) also happens to be
the aircraft with which I did my rating, which simplifies a
lot my complying with the insurance requirements. Actually
I did the long cross country (did my initial commercial in
a multi-) with a 310 -- but this aircraft -- or anything more
ambitious than the Duchess -- is now out of my reach in terms
of number of hours required by the insurances. For some
reasons insurances seem to keep moving the bar as I am
progressing along :-)

By renting I mean flying it solo or with passengers; some
places are happy to let you fly their multi- but only with
one of their instructors (e.g., to complete a rating), a
bit like what seems to happen with floatplanes.

Where are you flying if I may ask?

--Sylvain