I am wondering (assuming I have my choice of plugin's in a shop) is one better than the other.
It all comes down to wattage. P = IR; i.e., Power (Watts) = Amps * Voltage. If a given tool draws 14A on a 120V circuit, the same tool will draw 7A on a 240V circuit. The more amps you send through a wire, the thicker (higher gauge) the wire you need, as touched upon by Steven. Your tool will draw the same wattage whether it's wired for 120V or 240V.
Let me run through the rest of your question's components before coming back to the first part of your question.
I've heard that 220 will actually use less energy...
The reason we use high voltage transmission lines for power distribution is that power is transmitted more efficiently over long distances at high voltage. For a given amount of power, you'll lose a certain percentage due to the resistance in the line itself. As current (amperage) increases, the resistance increases (resulting in a voltage drop--giving you an overall power loss), but if we decrease the current and increase the voltage, we can transmit the same amount of power with less line loss.
That said, for all practical purposes, if you're running 1-phase power in a hobby shop or even a small production shop, the line losses from your breaker box to the tool will be insignificant and it won't make a noticeable difference whether you're running 120V (110V) or 240V (220V). Your electric bill will be the same either way.
One might be inclined to think that you should be using less energy because you're drawing fewer amps, but you're actually drawing power on one hot 120V leg and returning it on another hot 120V leg which is 180 degrees of phase with the first. The phase offset effectively doubles the voltage differential between the source and return, giving you 240V. A convenient (though technically incorrect) way to think about it in terms of what you see at your electric meter is that you're "drawing" that many amps from two 120V legs.
...and be easier on the motor.
I'm not so sure about this, but I doubt it. Maybe this is a misunderstanding of the difference between differences between different types of motors, or single-phase vs. 3-phase motors.
A 3-phase motor is simpler in design than a 1-phase motor because, as Steven mentioned in his answer, the 3-phase motor does not require a separate starter coil. 3-phase motors are also considered inherently more reliable by design.
If I can convert to 220, should I? Is it more efficient and easier on the electric motors?
If all your existing equipment does what you need it to do on 120V and you don't need any other equipment, there isn't really a compelling reason to install 240V circuits and switch your equipment over. However, if you plan on upgrading your table saw from a 1.5hp motor to a 3hp motor, for example, you will need to run it on a 240V circuit.
When you're shopping for tools, you'll often see that a tool can be wired to run on either 120V or 240V. If it's advertised as being 120V-capable, be sure to also check the amperage.
Usually for 120V, you need a 15A or 20A circuit. The maximum load allowed by code on a 20A circuit is actually 16A. Usually if the tool draws more than 16A, a 240V circuit is recommended since 120V circuits greater than 20A are not commonly installed in residential construction (at least, in the US). Upgrading a circuit from 20A to 30A isn't as simple as swapping out a breaker and receptacle, because to carry more amps, you also need a thicker wire.
Getting back to tool and voltage options--some tools, such as a bandsaw I was looking at a while back, are advertised as 120V/240V. However, in the case of that bandsaw, the tool actually required a 30A circuit in order to run on 120V. If you ever look at a tool like this and have to install a new circuit anyway, it makes more sense to go with the 240V circuit because it's more common to have a tool that's certified to run on 240V than one that's certified to run on a 30A, 120V circuit.