I was wondering what kind of ftp software are you guys using for uploading photos to stock sites, and why (what are advantages of the software you choose).

I'm using CuteFtp, but for example I do lack the possibility to set my files in specific order - for example first upload ss files, the dreamstime etc. (Or I don't know how to force the programme do it. )
Other nice feature would be closing the client to tray so when it uploads I don't have to have it on my main bar. (Which is usually quite some time...)

I use a shell script from the Mac OS X Terminal.  One command uploads images to all the sites without any further interaction from me.

I'm using Total Commander.Very fast, convenient and easy to use.
Just perfect.

I use Core FTP Lite because it's free and reliable.  In the past, I've used Coffee Cup, Filezilla, and a couple of others, but they at one time or another began to upload duplicates, and I couldn't figure out why.  Haven't had that problem with Core.

i've been a wsftp pro user for well over 10 years, but also use filezilla more & more -- oddly they each perform a bit differently - for images now i mostly use filezilla

Transmit on my Mac Pro, Cyberduck on my MacBook.  why different?  because I was too lazy to look up the registration code for Transmit when I reformatted the MacBook and just grabbed the free Cyberduck.  Both are great, but yes, the yellow duck icon is very appealing. 

I've also used WSFTP and Filezilla when I was on windows platform.  They are all pretty similar.  - better than comand line - which is what I've also used in the past. 

Filezilla and CuteFTP because they are free an easy to use....