the plot margins for cairolatex are incorrect. The bottom margin is far too big for the default settings, and the offset of the xtic labels is too small. See the following script which creates plots with:
1. cairolatex and default settings
2. pdfcairo and default settings
3. pdfcairo with fontscale 0.95 which gives the same h_char and v_char values as cairolatex with the default settings.
set xlabel 'xlabel'
set ylabel 'ylabel'
set terminal cairolatex pdf standalone
set output 'cairolatex.tex'
set terminal pdfcairo
set output 'pdfcairo.pdf'
set terminal pdfcairo fontscale 0.95
set output 'pdfcairo-scaled.pdf'
It seems like cairolatex has the same bottom margin like the 'pdfcairo fontscale 0.95', but they differ with respect to the left margins.
I tried to figure out what the problem is, but got stuck in graphics.c figuring out what determines the margin settings and where the difference between pdfcairo and cairolatex pdf is.