I have been a Linux user for 5+ years. I had used Debian, Red hat, Fedora, Opensuse, Mandriva, Mandrake, Linux Mint, Ubuntu, …. and so on. The distros that I always keep around are Debian running in an old machine and Opensuse dual booting with vista. However, I considered myself an advance beginner. But I want a challenge now. I was looking at Archlinux and Slackware. The only thing is that I will install it in my laptop dual booting with vista. I will remove vista to do that. Also I am learning python programming and bash. I just started today.
OK, so what I'm looking for is a system that allow me to learn Linux in a deeper way without obstructing my production side at least on windows. I will like to continue learning programming and the ins and outs of windows while it take me out of my comfort zone. That's is why I more incline to go with Slackware.
I would like to hear your comments, suggestions and advice on this. Is Arch Linux “better” or Slackware will be better for my personal situation? Please keep in mind that:
1. I want to learn python programming (I don't have any programming experience)
2. Learn Linux more deeply getting away from GUI or Yast more CLI would be nice.
3. Keep at least one partition on my laptop fully functional.
I will be waiting your answers... thanks

This doesn't make sense, if you remove Vista you won't dual boot with Vista.

1. Possible with Arch and Slackware (and any other distro).
2. Possible with Arch and Slackware.
3. Possible with any distro.

So in short, both distros will give you what you want, try both and and then decide for the distro you like more.

Thanks for posting, but after spending last night reading about between Arch and Slackware, I have the impression that the fact that Arch is constantly updating make it more unstable. While slackware tend to be more stable. Is that true or just my perception?

Arch is a rolling release distro, which means that the testing time for a piece of software is very short before it will be rolled out. This leads to the fact that software in Arch can (and will sometimes) break. Most of the time this is not that the whole system breaks, but that a specific application will not run or run with flaws. This will not happen when you run a stable Slackware release (but may be when you run Slackware -current, the development version).

It's great that you want to learn more, but why do you guys want to make it harder on yourselves? You can learn programming with languages like Python on any distro. People who want to mess with "advanced" distros like Slackware and Arch usually do so for philosophical reasons as much as anything else, it seems. Me, I want to make thins easier, not harder. I find it hard to be productive when things are difficult.

This is not about being more productive in the short terms, it is about learning how it is done with all the GUI tools of the "easier" distros. This is not only a great learning experience, it will also make you more productive in the long term when you have know problems to handle different distros because you know how it works under the hood.
To give a comparison to the hardware field: Why should anybody learn how the different hardware in your computer works and how it is put together correctly when they are vendors like Dell that do it for you?
Or a car analogy: Why should you learn to repair your car, when there are garages that will do it for you?

Some people just want to know how to do it yourself.

Edit: By the way, there is no real philosophical reason for me to use Slackware, I use it because it does exactly what I want, not more, not less, and that in a logical and easy to understand way.
And usually faster than those easy distros.
I can only thank Pat for building such a great OS and keeping it sane over all the time Slackware exists.