I didn't run that specific Stage 3 clutch, but in my SBC/Getrag swap I ran Spec Stage 2+, Stage 3, and Stage 3+. In my LS4/F40 swap I run a stage 4+.
The 6 puck Stage 3 held the power, but chattered like crazy, was difficult to drive in parking lots, and stopped recommending its use many years ago. The Stage 3+ gives you full face friction material vs. the pucks and had much, much smoother engagement and better drivability. Stage 3+ is the clutch I recommend most often.
The only differences between the stage 3 and stage 4 versions is stage 4 has the solid hub. I have put 36K miles on the stage 4+ and it has the same smooth clutch release manners as the stage 3+ I ran. So I don't think the sprung/unsprung hub has much to do with smooth engagement as they puck vs solid ring friction material does.
I used a SPEC Stage II in a turbo 3.4 application for a number of years. Good clutch but grabby and painful to use in a lot of traffic. I have since replaced it with a Stage II + and am very happy with the smooth performance of this clutch. I also use a Stage III + on a 3800 SC vehicle and am very happy with how it drives.
I have experience with both the stage 3 and 4 spec clutches in my 1998 fbody. Like guru said the stage 3 chatters like crazy and is not very streatable. I switched to the solid hub stage 4 and haven't had any problems since. I have way more control over the engagement with the solid hub. I don't have experience with the 3+, but I haven't heard of anyone complaining about it. I think it is probably a better option for anything under 400hp that us going to be driven a lot.