Grips are very personal things. I have a Robertson Fatal Styk, and have taken a deer with it. I tried to like the grip on it for years, but just didn’t. Although not usually at a loss for words, I found it difficult to express why I didn’t like it, so I never sent it off to be changed. For the same reason, I never tried to change it myself. Finally, I began to think about grips I like, like the Bob Lee, the Bear Kodiak, and the Black Widow, and figured out that I liked those because my hand stayed in position without having to force it to. With the Fatal Styk, my hand felt like it wanted to slip off the handle to the left. Once I figured that out, I determined that there was enough extra material in the grip to flatten out the part that touched my bow hand, and remove the curve that made me feel like my hand wanted to slip. So I did that myself, refinished the handle, and now it fits my hand like the others I mentioned.
It is likely that other Fatal Styk grips are not the same as mine, since they are made one at a time, and so may fit differently. It is evident that no two bowhands are the same. So YMMV.
I have never owned or shot a Blacktail, so can’t compare the two.