merc 261 nozzle are around 0.10mm bigger than the GTD one and have a different spray.I install some of these, and Im not sure if It's good, for sure that give more power, but with much more smoke.
But yes the MB nozzles do give more power, and more smoke. I compared the spray patters of both on my pop tester and honestly the shape is damn near the same in the first inch and half, which is all that matters for our eninges