DC motor instead of USM?? Confused!?

About to order the EF 75-300mm f/4.0-5.6. It says it uses a DC motor to power the AF, what does that mean. Because that one is 20 dollars more. Just confused. Thanks guys.

Basically, in the case of the 75-300 lenses, it means that the DC motor will be noisier. The USM isn't a whole lot faster or more responsive than the basic one.

I tried the 75-300 with usm and did not like the lens at all.

Slow apertures but gives good results in good lighting conditions, tends to hunt in low light... May encounter focusing problems if you ever use a TC with it...

Thanks guys, so pretty much just the USM one will be fine?

Well, usually the USM model goes for more. If your dealer's selling the USM for less than he's asking for the non-USM, then go for it. They're optically the same.