What is the difference between bottom and top swing derailleurs?

I just bought a cyclocross bike and discovered because of the cabling that I won't be able to use my front road derailleur and need to get a bottom pull front derailleur. As I'm looking for a bottom pull, I discovered something called bottom and top swing. What are the applications for these?

A roller is commonly used on cyclocross FD set ups to re direct
the cable coming down the seat tube,to run bottom pull FD.
it sits below the FD.. QBP sells band clamp versions.

top pull show up on MTB these days.. road STI brifters are a better match with Road FD.

Bottom swing and top swing is about the derailleur cage position relative to the derailleur seat tube clamp.

I prefer the bottom swing type (where the clamp is above the cage).

Sometimes the frame will dictate which you have to use. They'll be a water bottle bolt right where a bottom swing derailleur would have to mount or the seat tube might be flared where a top swing clamp goes.