I've an AMD A8 6410 @2 GHz with 8GB of RAM. This is my only machine and I use it for work purposes and multimedia. Former includes coding in C, Java, etc. , MATLAB programming, video conversions/encoding, testing stuff in VMWare Player/Virtual Box etc. And as for other uses there are watching YouTube, playing songs, watching movies and such. I used Ubuntu, Fedora, Mint before. A few months back I thought that if I move to lighter distros, my work will be somewhat faster. So I used Antix MX, Lubuntu, LinuxLight and I I'm currently using Cub Linux. But with all these distros I'm facing two issues compared to the mainstream ones :

1. execution time of processes are faster in the light weight versions
   
2. the light OSes fail to utilize all my CPU and RAM, my RAM usage never crosses 4 GB to 5 GB in them. I run VM OSes with 4Gb of RAM. Still my RAM usage doesn't cross 5. And a little load is put on them, the system crashes. For example, running VMware and using Chromium together, my system crashes. But neither my RAM nor my CPU was being overcommitted. CPU usage was around 30% and RAM was 4710 MB of 6940 MB. And also I don't know what Cub Linux did to one GB of my RAM.

What I need is a distro that works out of the box for internet and multimedia codecs and drivers and is still lightweight. For these reasons I'm not going for Arch or Debian since I'll have to spend time configuring the OS and drivers, whereas the programming environment and the databases take their own length of time to set up. I need to fix the crash issue or I will need to switch distros for which I'll gladly take recommendations.

I'll appreciate any kind of help, thank you.

P.S - I was thinking of giving Manjaro a try, but I'm being quite a bit apprehensive about it thinking about installing MATLAB in an Arch based distro !!!!!!!

The setup of debian is not that much (add contrib and non-free to the sources.list). But a minimal install does require effort to install all the related things not installed. For debian, most dev things are covered with packages (and deps of) build-essential and devscripts.

You're probably missing some power management features on the stripped down distros. Like acpid, powerd, cpufreq-utils, thermald, and such. Or use the bloated distros and stop all the things that you're not actively using. Printers (cupsd), scanners (saned), network shares (rpcbind/nfs-common/smbd), database server, web server, and on, and on, all installed and started for your convenience.

With systemd a few tricks:

$ sudo systemctl set-default multi-user.target
(to have a non-gui login, and otherwise choose your wm/de via startx and .xinitrc)

$ sudo service --status-all
$ sudo service cupsd stop
$ sudo service saned stop
(to stop services for non-existent hardware)

Plus all the other things that you're not using or lack the hardware for to need it. With inittab, and various /etc/init.d/<script> stop ways for non-systemd systems. Or systemctl stop <service> for partially systemd distros. Or combinations of all three depending on the distro.

Lots of options. It's all linux from a certain perspective. And you can still install stuff in non-distro ways that you want and doesn't exist in the package management system. With a little bit of know how you can roll distro specific packages and keep it clean.

Even if you find a preference you'll likely hop over little things. Recently I went from debian to xubuntu for ffmpeg over avconv. And then from xubuntu to arch because the features available in xubuntu for ffmpeg were not to my liking (-pix_fmt yuv444p, so yellow is yellow, not cream).

If you're running 32 bit distros, cresting 4GB ram might be a bit difficult. Plus other new stuff for new hardware that might not be available on longer release cycle distros. Without some effort to roll a kernel or other tricks. I often find that having more than one low end machine trumps vm's and one beefy machine. Networked audio, database under load, and other things that would make a single machine crawl in unpredictable and hard to track down ways. Or things that are just going to take a while and might be better served on the machine that doesn't make the room a sauna, or dim the lights.

I would recommend Debian, choosing the XFCE desktop rather than GNOME. I don't know what's going on with your problems with lighter distributions, though. I would think that whatever's affecting them would also affect the parent distributions (in this case, Ubuntu mainly it seems).

Additional setup which you probably want for Debian would be:

1) Append "contrib non-free" to each source line in /etc/fstab

2) Add the following line to /etc/fstab

3) run the following to get all your multi-media stuff loaded up:

Note that you'll get warnings about deb-multimedia.org, but that's to be expected.

Can you verify for us that the light distros you have tested were 64-bit versions? Memory behavior such as you describe can be characteristic of a 32-bit version on 64-bit hardware. (Saying nothing of the crashing, that is not characteristic of linux period.)

Yup they were 64 bits.

You probably meant /etc/apt/sources.list

Yes, /etc/apt/sources.list. Whoops!