For me it's the tab overflow behavior: Firefox has the left/right arrows and a dropdown menu, while Chrome just has tiny tabs: http://www.ghacks.net/2013/11/07/dealing-google-chromes-tab-.... And I have 31 tabs open now (sometimes 200+) so it would be a daily problem.
Not parent, but I've had well over two thousand tabs in Firefox + Tree Style Tabs before. They're usually accumulated over a number of sessions. If you don't open a tab, the page itself isn't actually loader yet, so very, very rarely are more than 100 or so actually loaded. Every now I'll go through and cull, but my browsing experience is never really inhibited by them.
For me it's 100% how I browse now, I don't think I could go back. I only open links in new tabs (which places them as branches in the tree) and it's a wonderfully useful spatial/temporal way of showing history, which is also saved between sessions (so bookmarks don't really replace them)