First, I am a big fan of Safariland speedloaders. I have used three since they were first introduced however many years ago it was, sometime in the 1970s I think. I have used only Safariland Comp l's in PPC competition since they came out and have never had any issues with them. They are much better for competition use than either HK or other twist knob speedloaders.
I believe that Safariland never made a Comp ll for the N frame six shot .357s. I have never seen one, nor a picture of one.
Now the rub. Safariland has not made the Comp l style speedloader for the six shot N frame .357 guns like the 28 or 27 in probably 15 years.
I have bought several at gun shows and found 3 new ones in a gun store a few years ago, and bought a few off of ebay. They are getting very hard to find. The last ones I saw at ebay sold for about $35 each.
Today, you can buy S.L Variant speedloaders for the N frame that act like the Safariland Comp ll speedloaders. They are excellent and expensive, about the same as used Comp ls on ebay! I have not used the Variants much, relying on the tried and true Safarilands I have, but they seem like they will be very dependable. Their advantage is that they spring load the ammo so they eject the ammo into the cylinder, rather that relying on gravity.
You have choices. Good luck with your decision.
As stated the advantage of the HKs are that they are made for so many guns and calibers so you can use the same system for many guns.