Fast R lens for differential focus effects

[Joe Berenbaum <joe-b@dircon.co.uk>]

Thanks to everyone who responded thus far to my questions about the two
versions of the 180/2.8 lens. What I'd really like some feedback on is this;
if I was considering a fast aperture R lens in the 80-200mm range primarily
to use for differential focus effects on static or near-static subjects,
indoors as well as outdoors, what would have the most out-of-focus
backgrounds and shallowest plane of focus and be most suitable, all other
things being equal? I think, off the top of my head, that the 80/1.4 would
be roughly equal to the 180/2.8 in this respect, maybe better, for
differential focusing. And it might have some other advantages, such as
being faster, smaller, and more convenient to use in confined spaces. Can
anyone who is familiar with these focal lengths and apertures comment on
this? I already have a 135/2.8 and it is a great lens but I want a more
blown-out-of-focus look than it gives. TIA for any comments.

Joe Berenbaum