The EF 24–105mm f/4.0L IS USM lens is often compared to the other L series zoom of comparable range, the 24–70mm f/2.8L USM, losing one full stop but gaining image stabilization (IS) in return, stabilizing camera shake up to three stops. It also has rubber gaskets for moisture and dust protection, although weather sealing is only effective if the photographer uses a weather-resistant camera body and a lens filter. Some early production models of the EF 24–105mm f/4.0L IS USM lens had a flare problem (reportedly the first 10,000 batch) and Canon offered to repair them for free.
The EF 24-105mm f/3.5-5.6 IS STM is a newer 'low cost' alternative to the EF 24–105mm f/4.0L IS USM. It has the same zoom range, but a non constant aperture range which is typical of many non-professional lenses. Both lenses have image stabilization (IS). The EF 24–105mm f/4.0L IS USM uses a ring type Ultrasonic motor whereas the new EF 24-105mm f/3.5-5.6 IS STM uses Canon's STM Stepper motor, which is quieter during video usage. The new EF 24-105mm f/3.5-5.6 IS STM weighs slightly less (525 g / 18.52 oz versus 670g g / 23.6 oz) and costs roughly half the price of the EF 24–105mm f/4.0L IS USM. 
On a 1.6x APS-C camera body, this lens' field of view is equivalent to that of a 38–168mm lens on a 35mm film camera; this is a very useful range, covering most normal to medium-telephoto needs.