Thank you very much Diego, for your interesting answer. I use Ubuntu on my desktop PC and I find it excellent. For a Linux in dual boot, I would try a lightweight Linux distribution (like Lubuntu or Puppy Linux). I tried CrunchBang and I think it's great because it uses Openbox instead of Gnome and Unity.
I tried Elemantary OS (in Live CD) on my PC and I find it excellent! I didn't succeed to install Linux in dualboot on my MacBook Pro, I need more time!
I am a big fan of Ubuntu as it is .deb based. I am able to run Windows programs if needed with Crossover and updated version of Wine. I have approximately 10 virtual machines (VMs) running for Backtrack, Centos, Fedora, Red Hat, Damn Small Linux (DSL), Lubuntu, and a few more. My laptop is a System76 which is amazing. If you use .deb based operating system (OS) make sure you download Alien so you can use .rpm files as well. I have attached a presentation I provided to a computer science doctoral consortium on Linux that you can download or view if interested. I hope I was of help.
Give Parallels or VMware a try. Overall, a virtual machine is much more comfortable than having to reboot to switch from OS X to Linux. And the impact on the system is (almost) negligible.
As for the distribution, I would suggest CrunchBang, which is a fast Debian-based distribution. But... why not using Debian, then? You don't really need fancy graphics effects, if you want to use Linux for real research work.
Stay away from Ubuntu: it has diverged too much from its Debian origins, and it almost impossible to update without itches.
Maybe a little late, I can however recommend you from my personal experience using Ubuntu. I have brought a mac book pro back-to-life with Ubuntu. Supposedly it required a motherboard change to be able to work again (according to Apple) so I decided to install it (nothing to loose there) and have been using it with 14.04 since at least half a year, with great results. My main problem has been with keeping hardware temperature, but there are great options within ubuntu forums (as Diego states, community is very supportive).
Dear Karim, thanks for your answer. Yes, Ubuntu is a great distribution with a large and nice community. But I don't like unity, so I use Ubuntu-gnome 14.04! I have now some experience with Ubuntu and Debian-like distributions. When I become geek I'll explore Archbang (lightweight and stable), since their Wikis are great! (but not suitable for newbies).
@Karim: How did you succeeded to replace your Mac OS with ubuntu? instead of using a virtual installation
Hello Mohamed, I am sorry to reply so late, didn't notice this update before. About your question, I chose to completely erase Mac OS from the computer, making a full install with Ubuntu Live CD. Thus, I don't have a dual boot but just a Mac that fully runs on Ubuntu, and until now it has worked perfectly. In my case my computer was useless with Mac OS, so I just started fresh. I'm still wondering why it works so good, despite being told that it was a hardware issue. Maybe Ubuntu just copes better with the problem instead of the frequent "panic attacks" of the Mac OS. BEst regards!