Steebo, the std and turbo plugs are different in the shape or unfinished there for, the std plug allows the the entire bottom of the plug to be exposed in the cylinder, a turbo allows this as well but in a much smoother more round finish, there is almost no interfierence when the plug is in the button.

3 port=Great all round motor, good bottom end power, great top with turbo head. i see this as more a budget motor, but is still competitive and able to win races just like the 5 and 7 just a little less overall power, but still strong for sure.
5 port= My fav, this is a powerhouse motor, more than enough bottom for buggy or truggy, and very good topend, it will run with any big $$ motor out there. They have awesome runtime are very reliable, and most pipes work great with them, i like the 2060 on mine and the 1005, the 2050 is ideal for small indoor tracks if you have alot of grip, no grip the 2060 is great.
7 port=very strong as well, just a bit less bottom than the 5. This motor has 2 more exaust ports and the main exaust port flow a little better, giving this motor endless topend, but is still very capable of powering a truggy with out breaking a swet, it is more smooth on bottom but can make killer bottom when clutched and piped correctly.

you can't go wrong with either one of these motors, the 5 and 7 are more pure competition bread, but the 3 port will suprise ya. The GO motor is changing the way people look at what you are getting for your money.

Hope this info was helpfull.