I've just run a test using Poser Pro on a 64 bit PC running Vista.

started Poser--Physical Memory usage 1.60G
Loaded a V4 character (58Mb) and deleted,  Did this 10 times.

Memory use after each delete was-- 1.65  1.67  1.69  1.68  1.69  1.69  1.89  1.70  1.70  1.70

Quit Poser and restarted

Repeated series but Shift/Deleted each time

Memory usage was-- 1.64  1.66  1.67  1.68  1.69  1.69  1,69  1.79  1.71  1.70

I see no significant difference between the results