I guarantee you that FF29's memory usage is better in general than FF13, because it avoids numerous bad cases where old versions that used to cause memory usage to skyrocket. Those cases -- where memory goes up 10x -- are the ones that hurt. In contrast, you're unlikely to notice 20% higher memory usage during normal use.
20%? Are we even looking at the same charts? After closing 5 tabs 270mb -> 480mb! Those numbers don't lie and your guarantee is worthless to those of us that have seen Firefox's memory bloat over the past year.
When Chrome started to get fat, it was great to have a lightweight alternative like Firefox. But lately even Firefox has been causing my 1GB netbook to thrash. I hate to have to junk a perfectly good machine that is only used for email and browsing just because of software bloat. After doing a factory restore, it looks like that or a lightweight Linux distro(while losing flash and HW accel) are my only options.
