speed of cacheing depends on terminal?

Hello,

1.5.17 with header caching enabled.  I've got read_inc and write_inc set to 1000.  Nevertheless, I've
noticed that the process of evaluating the cache (when I switch into a big folder) is significantly slower
when I use Terminal.app than if I use xterm/rxvt over Apple's X11.

This is puzzling, since I thought caching has nothing to do with the terminal choice.  Anybody know why this
would be, and/or how I can do something about it?

FWIW: I built using the BerkeleyDB libraries, since the other choices refuse to work with OSX.  (Actually, I
finally got mutt to build with gdb, but mutt behaved *really* weird with screen-drawing, so gdb is a no-go
on OSX).

Thanks.
-gmn