Last night was Sergio Corbucci 1968 night, featuring The Mercenary (aka A Professional Gun), which I'd not seen before, and The Great Silence, which is, in my opinion, among the greatest movies ever made.
There is, many claim, a thematic trilogy that concludes with The Mercenary and Compañeros. Wikipedia opens it with The Great Silence and in his interview on the Compañeros DVD, Franco Nero begins it with Django. I can honestly see the arguments for either.
I'm tempted to call it a tetralogy or even to call The Mercenary and Compañeros essentially the same part and blend them together as one concluding statement. This is not a wild statement, as they share far too many story and thematic points to be considered otherwise.
Nero and Jack Palance play essentially the same role in both. Nero's roles are respectively known as "The Polack" and "The Swede", although they sound like "The Wop" and "The Italian" respectively. The roles played by Giovanna Ralli and Iris Berben also correlate.
As direct comparisons, go, I think Nero is more interesting in The Mercenary, he not only has an awesome mustache, but he's given a bit more to chew on with the character. Palance is given more to chew on in Compañeros as falcon loving, pot smoking psycho. I think Berben may have more charisma, but Ralli's Columba is a more fully realized character.
That leaves the comparison down to Tony Musante, who does a fine job, and Tomás Milián, who is one of my favorite performers of all time, in what I think is what is one of his most delightful performances.
As such, I give the edge to Compañeros, although perhaps because I saw it first, but they are both very entertaining movies, and interesting companions to one another.