Half Stack Options
Whether you choose an angled or base half stack configuration is a personal choice between the different tonal qualities of each set up.
The MF400A (angled) is, in keeping with other angled 4x12" cabinets, tonally more aggressive than the base option. The angled cabinet is the usual choice for those who want a more prominent upper mid and treble response that really cuts through in a live situation.
Alternatively, the MF400B (base) delivers a more even mid range with less spread of the aggressive treble response. Marshall 4x12" base cabinets are more often used by professionals as they have a more focused bottom end and a smoother mid range and treble response. They are often easier to deal with in terms of sound reinforcement and monitoring in a live situation.