H2H, Fett.
Melee weapons, Din.
Use of suits? That's pretty vague. Does this include things like the whistling birds, Fett's wrist-mounted micro-rocket launcher, Fett's hidden blades, ect? If so, I'm inclined to say Fett. I don't think the whistling birds can pierce Mandalorian armor (given the most recent episode).
Firearms, definitely Fett. Not that I feel either could do very much to each other with conventional firearms. But if it came to, say, a target-shooting showdown between the two, Fett is unquestionably the better marksman.