What will be the best for school mac? My course is mechanical engineering now what is the best, iMac with 5k retina or Macbook Pro 15 with retina? ASAP.

Hard to answer a question like this. But a college student usually needs their computer to take up minimal space and be very portable. So a laptop would be my choice. iPads are nice but you need to make sure that the iPad will perform the tasks you need it for.

Some engineering programs only run on Windows. Check with the universilty FIRST. You can run Windows on a Mac, but each option affects your purchase decision:

1) Boot Camp

Pros:

Runs natively so is very fast; stable

Cons.

• You must partition the hard drive allowing at least 80-100GB for the Win partition. Current MBPs that have only SSD drives don't have a lot of hard drive capacity to spare unless you buy the top-of-the-line model with the 512GB SSD--a very expensive option.
• You have to reboot to get into Windows or, once there, back the the Mac side

2) Emulators (Parallels; VM FusionWare)

Pros:

Switching to Windows is like switching Mac apps; no need to reboot

Cons:

• Emulation mode is always slow
• Win apps needing accelerated video like 3D Engineering rendering programs may not run properly
• Although you do not have to partition your hard drive, the emulator wll take quite a bit of space.

And either way, you will need to order the MBP with as much RAM as available. You cannot upgrade RAM in Retina models beyond what the factory installs.