Is there some reason for Slackware ship gFTP instead of for example FileZilla.

From what I know FileZilla e more develop and maintained than gFTP.

Which one is better?

Because Filezilla won't build on a stock Slackware installation.

From the Filezilla's SlackBuilds.org entry:

I suspect that building the latest version of Filezilla is even more problematic.

I see, I didn't know that.
And between the two, is there some big difference in performance or functionality?

The performance of an FTP client program depends much more on the network than on the CPU. You're network bound unless the FTP client is badly written. Personally, I find gFTP to be very simple and convenient. It lets you bookmark sites and the interface is as easy as it gets.

My only complait is gFTP don't look like an active project.

I'm pretty sure it's active, but gftp is a mature project due to the fact it's been around for ages. This means almost no new features and few releases.

The FTP specification is also stable, so there's no new development on that end.

It's true that FileZilla will not buildable in default Slackware installation since it requires wxWidgets, but all of the requirement are already provided in SlackBuilds project.

FileZilla 3.3.4 will require another optional package: tinyxml
If you don't have this package, you can use builtin package provided by FileZilla.
My slackbuild update for FileZilla is still in pending

Oh... it has been approved just now
http://slackbuilds.org/repository/13...ork/filezilla/

If you use firefox you might also try the "FireFTP" add-on.

I needed a graphical FTP client some months ago, so I tried first gFTP.
The results where NOT good : gFTP kept crashing silently in matters of minutes, on any of my stock Slackware boxes (12.2, 13.0 and Slackware64 13.0).

So I tried Filezilla with wxPython and it's rock stable. I use it since, mainly to do FTP/ES.
Packages building and upgrading from Slackbuilds.org is straightforward for both.

As a side note concerning Filezilla 3.3.4, I had to use the builtin TinyXML because it complained that TinyXML 2.6.1 (latest version, packaged with Slackbuilds.org) is broken.

Everyone should learn to use lftp. Nothing wrong with a graphical client, but lftp is just so efficient and fast.

Or ncftp. Tabbed completion on filenames is nice.

I have both installed, gFTP and filezilla and both are working stable. Sometimes I use MC also

Thanks for the info. I have checked and yes, it's broken now. All we can do is wait until the maintainer of tinyxml updated his package as it's his authority to update/patch the package.