It's not something I ever do, but I imagine the answer to your question is that you can easily search for a particular tab when they are all in one window, but it would become a big chore if you had to switch between multiple windows and search each one to find a tab.
>>Digit-+(OP)
On Firefox, at least, search will surface tabs in other windows. I often have 2 browser windows open, one for each monitor (one mostly for streaming content while I dick around on the other one).