I wish flat handles similar to those used with vintage injector razors were available for safety razors. I think flat or faceted handles allow for better control of the head.
After capably shaving many times with the super-slick Futur, I realize I can shave with pretty much any razor handle, faceted or smooth…
I actually prefer the round handles like on the 1912 Damaskeenes, early 1914's, Micromatics and Streamlines.
I like a solid razor handle round or square. The one that came with that Utopia is my favorite for now with a Merkur head.
I prefer thicker and heavier handles, and have never noticed and big difference with regards to shape or texture. To be fair I have not tried one of the really smooth "Futur type" handles...
Ah, but wet razor handles can be—particularly if they are smooth & shiny! Slippery When wet! ...And Painful!
For years the only razor I used an old type head on a hex handle, but lately I've been using a single ring with a round handle and I haven't noticed any difference in control.