There are multiple constructions that are called "MAPROM" so this is hard to answer. First, some turbo boards offer "MAPROM" through a custom glue-chip. Many GVP boards have such an additional logic on board. The drawback is that such add-ons are hardware-specific, so you depend on the software of the board vendor, and second, such add-ons are typically not able to write-protect the ROM mirror, and they can only select from a small set of RAM locations where the ROM can be mirrored to. If all these locations are used, the mirror cannot be applied.
Then, many Amigas include a memory management unit, as part of the MMU. This goes for the (full) 68030 (not the 68EC030), the 68040 and the 68060. They allow generic manipulation of the MMU table (e.g. by the mmu.library) independent of the Amiga make and model of the turbo board. The MMU also allows to write-protect the ROM mirror. There are a couple of additional tricks the MMU can play despite mapping the ROM.
Other than that, the two options are equivalent as they allow to redirect ROM-accesses to RAM, which includes typically a speed-advantage.
