I prefer the simple operation of the Safariland Comp I speedloaders. I've used the HKS but didn't care for them.

As for grip clearance, it can be hit-or-miss. My Spegel boot grips have no clearance problems with the Comp I. I have a set of Eagle Secret Service grips that block the Comp I. The current S&W OEM rubber boot grips kind of binds on the Comp I (I can line up the rounds and get them loaded, but the loader doesn't always fall free). I have a set of PGS Hideout grips that had to be pretty heavily modified to work with Comp I loaders.

While it may not be the best option, you can always modify your grips to allow for speedloader clearance if you find a set you like but binds up on loaders.

Or you can use speed strips and not have to worry about what type of grips you use.