The first of the two reviews listed below directly addresses moon-clips and speed loaders for the 627 5", but does not get into speed loader brands. The second might, I have not read it in years.
As a former PC 627 5" owner, I suggest that if you are loading .38's, than the moon clips are faster than a speed loader (mine were S&W full moon clips bought from their web site); however, if your loading .357 magnum, those loads are too long and heavy, and the moon clips are not stout enough to hold the bullets relative position to the eight chambers because they collapse towards the center. With .38 this is not an issue at all.
I competed successfully with the 627 in IDPA with full moon clips in Anniston, AL, but it was unofficial because the 5" barrel exceeds the maximum allowable, and I didn't follow the 6 shot maximum for revolvers. I was just working on proficiency. People loved to look at and shoot that revolver.
I'll also tell you that at least two reviews have noted that with moon clips the pistol is slightly more accurate, but would probably only be an issue with hunting applications. I never noticed a difference. The trigger action was pretty good as delivered, but I had it tuned some more.
I bought the cheaper of the two Perf Ctr holsters made by Desantis for the weapon off of the S&W web site, worked very well. Very intimidating gun compared to the Glock 22 my agency requires, but I never used it in an LE context.
Finally, I found Jerry Miceluk's (spelling) instructional DVD indispensable for firing a wheel gun fast.
A very positive review of your revolver is at:
Handguns Magazine and another that is critical of the weapon for IPSC speed gun competition but otherwise favorable is at
December, 97 IPSC.