As a former Reduced (ref. 3510.50) owner here's my 2 cents...
What I liked about it
*Great size (top lugs to bottom lugs distance...and the overall height of the watch as it sits on your wrist) for people with smaller wrists
*I loved the bracelet. I has a nice taper to it. The mixed links/surfaces with both polished and brushed surfaces really dress the watch up. Slim clasp allowed multiple positions for micro adjust and never felt like it added any bulk to the bottom of the bracelet.
*Costs the same to service as a Speedmaster Pro
*About half the price of a Speedmaster Pro which eases the "clench" factor for people just getting started in the hobby and haven't normalized spending $5,000 - $10,000 on a wrist watch. At the time when I had bought my Speedy Reduced I had never spent more than 5 or 6 bucks on a watch....so tripling that was a big jump for me at the time.
*These were available in tritium and look very nice once they start to patina
*This was not a daily driver for me, but if it will be something that you wear most days of the week, the automatic / self winding movement is a nice convenience to grab it and go in the mornings.
What I disliked about it
*The reference number I bought had the little minute numbers at the 5, 10, 15, 20, etc. minute markers. This didn't bother me much at first, but after spending hours on the this forum and other sites looking Speedmastesr it did start to bother me that mine didn't look like the "real one", and ultimately was one of the primary reasons for me selling it for a Speedy Pro. (If you go with the ref# 3539.50, as suggested above, that won't be a problem since that reference omitted the little minute numbers....but those 3539.50 references are the highest priced out of the black dialed Reduced lineup and that point I think you may as well just spend a little more and get a Professional.)
*The crown would occasionally, and just ever so slightly, dig into my wrist
*The subdial spacing seemed kind of off since the hour markers at 3 and 9 are greatly shortened.
What's your primary reason for gravitating towards the Reduced vs. the Professional?