Reasons for motor shield? (general question)

Hi, I'm curious why someone would use the Arduino motorshield, rather than building either a transistor H-Bridge, with a seperate power supply for a dc motor, or using relays to separate the power supply for a servo motor. Is it just easier, or part of the Arduino system? I've noticed the heat sink on some of them. I've never used this to power motors. Generally speaking, am I missing out, by not using the motor shield?

Thanks

Oh!, and additionally, how much current is required to pulse a servo with PWM. Assuming a series of motors are all expected to move in exactly the same way, couldn't I use one arduino pin to send pwm to all the motors at once?

I think shields are just a connection convenience. Any motor shield is just an implementation of some or other driver that happens to be on a shield to make it easy to hook up.

On the other hand, I have a Pololu 2130 which isn't on a shield and is just connected by wires.

how much current is required to pulse a servo with PWM

Need to check the specs on your servo. '328P can output 20mA before signal level starts drooping due to excessive signal load. If your servo needs 1mA to make it switch high & low, then 20 would be the safe limit. If more current is needed, then you could buffer the signal to help with drive.

Thank you both!