I'm not 100% familiar with the 500.. but my Stilo came with a single piece centre and rear silencer. Presumably a single piece, fitted to the car before the rear subframe went on, is cheaper/easier to build.
Replacement silencers have a short piece of pipe as in the first picture above, so that you can remove the exhaust without dropping the rear sub-frame. It also suggests that when the original silencer dies, you are supposed to cut the old centre pipe in the right place so that it meets/slightly overlaps the shorter pipe on the new silencer. The new silencer has a flared part (as in the picture) which would fit over the old pipe, so you have to cut the old pipe to give 5-6cm of overlap.
The second silencer appears to be a variation of the same principle. It looks like it's designed to fit to a system where the centre pipe has been cut (just closer to the silencer than the first silencer requires).
If the 500 stock silencer looks like picture A (i.e. it's got a separate rear silencer as standard) then you would have to keep the pipe part, but cut off the silencer, to fit the new one instead. This would give you two joins instead of one, so doesn't appeal to me for aesthetic reasons.. but technically it works the same.
If the 500 stock silencer is a single piece from the cat back, then you would have to cut it somewhere to replace the silencer.. so the second silencer isn't any more or less trouble than the first one.
Arguably the second one is neater, since you don't have to mess about with feeding the new curved pipe over the rear sub-frame... but the join will form something of a "hinge" so it may be trickier to seal, especially since space to add a clamp might be restricted. The "looped" pipe isn't too tricky to replace on my Stilo.
Ralf S.