Unidentified subject!

[Gregory L. Hansen]

If I'm shooting in low light conditions and I have a longer lens at f/4
and a shorter lens at f/2.8, is there ever an advantage to using the
shorter lens for the wider aperture, but a slower film speed, and then
cropping and zooming on a portion of the picture?  I do I pretty much
always want to make the picture as big as I can and use a film appropriate
to the lighting (which is probably 1600 speed)?