Almost every day I use both of them. They both have pros and cons. It's all about having practice and spending time on any of them. But one thing for sure is a game changer that is FF dev tools can show you the events bound on element right next to it, unlike chrome's list of events.

My recollection is that both are as bad as each other: spiteful UI with 1 watch window and a fixed window layout. Dear people - start demanding more from your tools.

Going back on topic, I've stuck with Firefox for years because of DownThemAll and Firefox Sync. But I stopped using sync a couple of years ago, so that just left DownThemAll... which won't work after this change. So I'll probably leave Firefox behind. Safari supopsedly gives you better battery life on OS X, and Chrome is more popular (i.e., people probably test their stuff on it).

DownloadThemAll will work now and into the future with Pale Moon.