What are the differences between these tuning machines?

Question

I just got a used Fender Starcaster S1 to compliment my existing Behringer strat. Upon inspecting it, I noticed that it has different backs on it's tuning machines. What are the differences between these besides appearance?

Answer 1

Inside them both you have a cog and a worm gear, which works as per this gif from Wikipedia:

Worm gears have a very useful property - they can cope with high tension without slipping.

The casing differences are purely cosmetic.

Answer 2

There are some easily noticeable differences:

1. The ones on the Behringer are attached with screws on the back side, while the ones on the Fender have a nut on the front.
2. There might be differences in the string attachment itself (not pictured here).

Some differences are not so easily spotted, and may or may not apply:

1. Differences in gear ratio, some of the higher end tuning machines have a high ratio so you can easily do minor adjustments in pitch.
2. Differences in build quality.