There are so many... which one is "better" and why?

www.realvnc.com
www.tightvnc.com
ultravnc.sourceforge.net

etc...

Any ideas? Basically, I'm looking for something simple that I can "send" to our clients for when we need to "walk them through" some steps, etc...

So it must be simple to install and set up on the host side.

Thanks!

Here's another one:

www.tridiavnc.com



Arg! Which one should I use? I just want something brain-dead simple for the "mother-in-law" type of clients who need hands-on support.

Any ideas?