"Cheap" is relative so can't help you here. Mk1 is about 13 yrs. old and Mk2 fixes the faults or better word...improves on this
popular lens. L lens is pro quality meaning durability/weather sealed and reliability. It's constant F4 is also good for video.
Mk1 is sharp for APSC sensor but soft for fullframe while Mk2 is sharp for apsc and fullframe (that's the improvement)!
As a 5X/times zoom ratio this type of lens has it's handicaps..better than words like deficiencies or weaknesses but this is a result of
the physics of optical technology. It's good for a walkabout or all-in-one lens to take along for general use. Another lens you can consider is Sigma 24-105 F4, no weather sealing if it suits your style and use but is heavier and bigger with cheaper price like all 3rd. party brands.
Retrospectively, what camera model are you using can also dictate which is a more valued buy....I haven't hear of cheap with warranty, you might have to forgo one of these criteria. You could check out Peninsula Shopping Centre..