Also, were you printing the same or a different negative? Unless
you have mastered exposure and development, they probably vary
in density. Films have different base fog, as well.  Not being
sure if you were printing at the same aperture, could easily
account for it as well. A 5 second exposure at f4, would be 10
at f5.6, and 20 at f8.  I usually aim for more than a 10 second
exposure, it makes burning and dodging easier.  Keep notes!! I
write down the paper, the height of the enlarger, the f stop,
exposure time, burning and dodging (with a diagram), and notes
about development, if anything other than Ilford MG for 2 min,
for each print.