Skimmer with pump below or pump on side

There may be a simple answer to this but is there any major difference in skimmers where the pump is below the skimmer vs pump that is on the side?

Is it simply a footprint / space issue?

If both are about the same height does the one with the pump below suffer from the water being in contact with the bubbles for less time?

Currently looking at the Bubble Magus 5 / 7...

Thx