I use etr7 as it was available when I started loading 40 s&w , I look through loading manuals , compare and then start working up a load .
Length comes into play for me with what fits and chambers , have not used Unique in 40 caliber , and since I ran out I am going with other powders for the time being in calibers I used it for.
Started tumble lubing 40 s&w and am now powder coating for the Glocks , models 22 27 and 35 , fun caliber , molds I am using are MP and NOE , hollow points , 155 to 185 grain , Those police trade ins are mostly good buys .