Interestingly, the magnifier highlighted by TheQ gets better reviews on Amazon than the other one.
As a former professional user of magnification for work, with magnification greater than around 4 you will find the working distance too close. My own preference is 2.5 but good lighting is essential whatever magnification you use.
Many of the cheaper magnifiers do not have great optical quality, my own preference, apart from expensive, progessional precision magnifiers, is a Lactona Loupe (available from some dental suppliers) lighter and less clumsy than Optivisor and a similar price.
Jim P