I'm still using portable versions of Firefox and Thunderbird, simply because I can easily transfer them to a new PC or Windows installation, without having to jump through any hoops or use an online service to transfer my bookmarks, add-ons, messages and settings.

The software is the same, apart from where it saves its data, which has no impact on operation or performance. On it's own, it's less convenient and it's easier to be 'messy' with portable software, if you don't take care to carefully place it in appropriately named folders. The disadvantage of portable software is that there is no installer that automatically creates shortcuts on your desktop, in your start menu and in the list of installed software. With the start menu of, I even had a comfortable menu instead of having to go through folders. I could use a better browser than the mandatory Internet Explorer on school PCs. That way, I had my favorite software with my settings, bookmarks and private data, which would also leave no traces on machines I used them on. Back when I was in high school, I had a thumb drive with portable versions of Firefox, Open Office and various handy tools with me at all times. Portable software can be taken with you, e.g.

Moba portable