As far as I know -
Drop floor plate, internal box magazine
* Less chance of feed problems as feed rails are part of receiver.
* Adjusting rails to handle different cartridges is permanent.
* Nothing to lose.
* Unloading can be slow or awkward with gloves.
Detachable magazine
* Feed lips part of magazine, can be adjusted for slightly different cartridges if you rebarrel and it isn't permanent.
* Magazine can be lost, disabling rifle (unless you have a spare with you).
* Loading / unloading is faster, fairly easy even with gloves.
There may be more, but this is what I came up with on the spur of the moment...