its not a question of what it can do per se, but rather a question of what you can do with it.

Mac is a "walled garden" a so called Closed platform. Linux is a community, a veritable brotherhood of like minded people who believe in freedom and equality(though they can be pretty childish at times :D, like this

)

If you are buying a Mac you don't get to choose, beyond a few company policy determined things, what processor you want or what gpu you want, how much ram you need etc. That is the problem of choice, you have no transparent choice.

"Mac runs better than windows" one of the reasons is that when apple builds the kernel for a mbp they know the exact capabilities of the machine they are building for so they are able to build a leaner smaller kernel then windows which must support a plethora of devices.

Linux goes a step beyond. If it is a computer that C can be compiled on. and C has been compiled on pretty much everything in the last 30 years give or take, then you can build linux on it. You never really need to throw away your machine, whether its an atari or an amega. People can and do install linux on these machines and more.

Linux is more powerful simply because it unfetters you. It gives you the tools in the sandbox of systems computing and administration and leaves you free to do what you want to, what you are capable of. Of course if you don't know enough or if you make a mistake it would be a nuclear holocaust as far as your pc is concerned.

however this is where the community aspect of linux comes through. most of the time you would find, that somebody has already written the program that you need and they have shared it for free and whats more, they have included the source code, so that you can customize it according to your needs!! if you have a problem or a breakage just google!! most probably others have had that and there is already a solution either on a forum like Ubuntu Forums, Arch Linux Forums.. or if its a common problem then on the news page of your distro of choice. If not then don't lose heart, file a bug report! Help would get there, maybe not immediately, but eventually... and at no point of time do you have to spend a single ruppee!

It is not about what mac can do or linux can do, but what you can do with it.