justfitme

The external cups (BB) means that the bearing clusters placed outside of bottom bracket shell (in comparison to octalink/square taper battom brackets that placed inside the shell).
External bottom brackets gives you more stability and stiffness feel.
Plus they generally lighter.

In my case I switched from Acera crankset to one you have in the link and the difference is huge in feel and weight (250 g difference).
Many professionals saying that there is not much difference between Acera/Alivion and old internal BB Deore or LX.
But it is not entirely true - Deore lighter I isntalled on my wife's hybrid Deore M510 and it is 200g lighter than Acera.
Plus you may get better bottom bracket replacing the "priceless" stock one.
The professionals saying this mostly because there are External BB's on the market and everything not external is a crap by default.

(Deore M510 twice cheaper than the one from ebay you are showing).