Justin is a "stand-up" guy whom I have a lot of respect for regarding both his skills and integrity. He has made some customs that I love and I am currently in the market for one of his hawks. (Wood handles. Not the RD or the rescue hawk.)
Just like there are deep divisions of opinion regarding those who like mags and those who like standards in the Busse line, there are grips out there to fit any malformed, mutated paw. Many Busse grips, I like; many I don't. I got along great with virtually all of the Swamp Rat with only a notable exception or two.
I was completely unable to use the RD grip. It was thin and didn't fit my paw at all. The first RD9 was back when they were a low, obtuse (?) saber grind. Darn near a hollow grind. Every time I tried to chop, it shifted badly in my grip. Most likely a combination of the grind and grip. I later had more of a flat grind but still couldn't adapt to the grip. That was my experience only, many find them very comfortable. (Many sing the praises of the EU grip - I couldn't use it.)
The 5160 steel? I think Justin does a great job with heat treat. I never abused the rd9 to the point that I saw any deficiencies.
SR101? Abused it a lot!! I might actually like it better than INFI. (They might take away my HOG card?!) It is less corrosion resistant but I find it easier to sharpen.
The RD series is somewhat cheaper to purchase - I would definitely call it a bargain. The fit and finish isn't to the same level as SRKW. As a user, you may not care... or you may.
Either way, both are solid folks producing a great product. Like I said, Justin will get more of my money soon in a hawk. The standard RD series didn't work for me at all.
The first RD9 was ground like the big RD pictured here.
My RD before I traded it...
Now, there was a Custom 3V with formed g10 grips at Blade '06 that I
greatly regret not buying!! It felt fantastic! The fit/finish/feel were amazing! It was $350.
When it comes to grips, few things have ever felt better than the ol' Ratweiler and Dog Skinner, though!!