They're the same basic concept: Two continuous CFL bulbs inside similarly sized and (apparently)¹ similarly constructed soft boxes.
- The most obvious difference is that one comes with three backdrop cloths and a stand to support them. The other does not.
- One uses 50x70 cm softboxes, the other uses 50x50 cm softboxes.
- One uses a single 135W Continuous Fluorescent Light bulb inside each 50x70 cm softbox, the other uses one 65W (CFL?) bulb inside each 50x50 cm softbox.
- The smaller 50x50 cm softboxes have no internal baffling. The listing for the larger 50x70 cm softboxes do not reveal the internal design of the softboxes, but I would be quite surprised if, for that price, they had any internal baffling.
- The smaller 50x50 cm softboxes are lined with a reflective silver finish. The listing for the larger 50x70 cm softboxes do not include photos of the internal lining but states that the box is 'black' in color and made of 'aluminum'. This may be an indication of the type of reflective lining.
- The lower priced set tells us the maximum/minimum height of the light stands. The other set does not. Neither listing gives the maximum load capacity of the light stands.
In general larger softboxes produce softer light when placed the same distance from the subject, or can produce equally soft light when placed proportionally further from the subject, than a smaller softbox. But in this case the size difference isn't very significant and the way each one is made might actually allow the smaller one to produce more even light than the slightly larger one. Or maybe not.
Wattage is not the only thing to be concerned about with continuous lighting, particularly when CFL bulbs are used. One must also consider the range of the visible light spectrum that each can output. It does not appear (I don't read French very well) that we are told the CRI (color rendering index) of the bulbs in either set.
A light source, such as the sun or an incandescent light bulb, that produces the full range of light in the visible spectrum has a CRI of '100' because it produces some light across 100% of the visible spectrum. Other light sources that create light by passing electrical current through a tube filled with gas, such as a fluorescent bulb, can have CRIs ranging from 25 for high pressure sodium, to 95 for a tungsten halogen, to some very specialized (and expensive) gas filled bulbs that can produce as much as 98% of the visible spectrum.
Most CFLs have a CRI of around 75-90. 90 is marginally acceptable for showing the accurate color of many objects. 75 is dismally inadequate. Anything with colors in the missing portions of the light's output spectrum will not be accurately reproduced. Based on price alone, I'd guess that the cheaper set that includes the backdrop and larger softboxes has bargain basement bulbs with a relatively low CRI. The other set might or might not have bulbs with a higher CRI.
One set has bulbs that are roughly twice as bright as the other. This can be an advantage or a disadvantage, especially when creating images with a non-controlled background. The lights could be too bright in relation to the ambient light illuminating the background when the softbox is close enough to give the light from them the angular size one desires. Or the lights in the softboxes may be too dim in relation to the ambient light illuminating the background, even when the soft box is as close as it can be placed without appearing in the frame.
Not knowing the internal design and color of the reflective surfaces of the 50x70 cm softboxes make it difficult to compare them to the 50x70 cm softboxes. Either one could produce a more concentrated 'hot spot' in the center of the pattern of light they produce, while the other could be more evenly dispersed. Without knowing what the inside of one looks like, we can't even begin to predict which is which, or determine if they are both very similar.
