Garko and Steffen were the first SW stars after the better known mainstream guys (Eastwood, Van Cleef, Nero etc..), that I was exposed to when I first got started in the genre. I've been big fans of both of them ever since. They are about equal in my book, but I notice that Garko is much more popular and widely loved by fans of the genre. I like both of them about equally, and I like them even more than more well known guys like Nero and Terence Hill and Tomas Milian.
Some interesting stats:
I have seen 19 SW's starring Steffen, and I like 16 of them (84 percent). But only 1 of the 16 is in my top 20 (6 percent).
I have seen 13 SW's starring Garko (Haven't seen Bad mans river yet), and I like 9 of them (69 percent). This is a lower ratio than Steffen. And I like nearly twice as many Steffen movies as Garko movies. However this is made up for the fact that 5 of Garko's westerns are in my top 20 (25 percent).
I guess the story is that I like Garko for quality, and I like Steffen for Quantity. The other conclusion I draw from this is that since Steffen made so many westerns (27 at last count), even those who are not fans of him are bound to like at least one or two of his movies. Its murder by numbers.