Which to learn: Unix or Linux?

To run on an intel platfrom Linux is the best. Sun creates Solaris for the intel platform, but the risc platform is still the strong suit for Sun. You will get better performance for your RAM from Linux. CPU is usually not an issue, unless you are doing a lot of number crunching or nested algorithm functions. All offer guided installations and default settings now so the install process shouldn't matter. Linux offers the most software and drivers from the install CD without needing to getextra downloads. However, tech support will be much better with Solaris. Linux is focused on development and since developers are always changing things and need to modify code the Linux support system isn't that great. Its hard to support something when you have no idea what was done on the other end. You could always post on boards like this to get Linux support, but Solaris (Sun) will have the better vendor support. If it is for home use/learning I would go with Linux. For production servers I like to stay with Sun Solaris (HP-UX and IBM's AIX are also good) because of the support fact and a few other reasons, mainly because Risc hardware is more reliable and performs better in my opinion so I like to use software that is best ported to Risc servers. Although Risc is usually more expensive, depending on what you need. Only for the most high end performance specs can you get Risc cheaper than an equivalent Intel setup.

In another note just FYI - Linux isn't going to be so open much longer. Many of the vendors (all that you mention) will soon be releasing core OS only and selling the additional packages. If you choose Linux I would go with Red Hat. They are the most common so you will find it easier to get information, drivers and help. They also seem to have a decent support group compared to Corel. SuSe isn't bad either.

Hope this helps. Good luck.

I agree with the previous answer on the benefits of each of the flavours on Linux/Unix.

What is it you are trying to achieve? Do you want to learn Unix to a level of a professional administrator, or are you trying to learn for home use only?
Ifyou are interested in using Unix professionally I would go with Solaris on Intel. Even though the risc platform is where Sun's strength lies, there are substantial differences between the Linux and Solaris distributions. There is limited software compiled for Solaris Intel (a good site is www.sunfreeware.com). This provides you with a great learning opportunity as you will need to compile a substantial amount of software.
If you are seeking an introduction Unix I would recommend RedHat Linux. This is probally the easiest version due to support, the software distribution and the user interface. You will find it easy to convert across. One of my junior administrators, with experience only in the Microsoft products, had an intel machine set up and functioning in a couple of hours. Within a week he was comfortable with the OS.
My personal preference is Redhat for home use and Solaris on the sparc platform for enterprise use.

Cheers
Peter

I just wanted to put in my vote.

I agree with the answers above. Red Hat is the way to go. Plenty of information, books, and support.

Once you become a pro then you can try other's. FreeBSD for example is also a popular chioce.

This is pretty much a choice of taste on your part. Linux and Unix and indistinguishable from a OS point of view, and both should just be considered Unix. (The differences between them are on the same level as the differences behind IRIX/HPUX/Solaris and AIX, yet their all considered Unix).

Sun Solaris gives you a up on the career path, as it seems to be the one with the largest install base. Its tech support is excellent, and its machines cover the range from PC class to world class servers.

Linux Redhat would be my second choice. Its gotten to have a excellent installation and administration interface (better then solaris) and seems to have been adopted as the Linux for the business community (IMHO).

The knowledge gained from either is transportable to the other, so its largely a question of taste.