No they aren't, regarding specifically the file system.
If you follow the discussion beginning with
this post you will see that what matters is only the quality of the USB thumb drive. And unfortunately it is hard to know and I don't know a reliable way the check. It seems that ext2fs be not very useful in that case. So my advice is: don't put on an USB stick files that are very important to you, unless you make frequent back-ups. And choose carefully the media looking for a guarantee. Not all expensive ones are good, but very cheap ones are probably crap, that will wear out soon, and maybe aren't even able to give you the advertised space.
Long story short: don't put a critical system on a thumb drive.
