When using the menu-driven PDF export in the QT terminal, the page size is chosen as a portrait A4, which does not look like the gnuplot window at all. In addition, the actual plot graphics is then located on the upper half of this A4 page.
When using the menu-driven SVG export in the QT terminal, the resulting SVG file has a landscape format, but not of the same aspect ratio as the gnuplot window, and there is too much white space on the right hand side of the plot graphics content, and also too much whitespace below.
When using the menu-driven PNG export it looks correct.
I'm using Gnuplot 4.6 from Debian Sid:
ii gnuplot 4.6.0-8
ii gnuplot-qt 4.6.0-8