I've had the SBDX017 and the SLA021 and I prefer the SLA021 by a distance.
I am a tart for the SBDX001 but I only ever notice MM or Prospex on the dial in pics. Never in real life, so don't see the big deal and prefer the upgrades anyway.
I had one in my basket after I replied to you and was hoping you had somehow managed to double dip two offers and I wouldn't be able to resist.