The MP40s move water differently than the Tunzes. I run a few of both in various tanks - The best analogy I can provide is the Tunzes move a stream of water....whereas the Vortechs seem to move virtually the whole water column.

The only downside I see with the MP-40s is that they can be a bit louder when run near full power.

That said, I think you'll be amazed at what 2 40's will do in your tank.