Canderous...
More fighting experience, grew up in wars trained his entire life to fight wars, and became the most famous bounty hunter in the outer rim. Thats something in that time when you see how many there are, later on he becomes Mandalore and he's damn powerful and good with a blaster.
Canderous takes this because of experience.
If there's anything in this fight that gives Jango the advantage, it's his jetpack and the sheer amount of weaponry he has. If the going gets rough, and it will, he can always jet away and fire off a nice rocket towards Canderous' face. That, coupled with his ability to use those twin blaster pistols and his various hidden weapons and gauntlet attachments, especially compared to Canderous' single heavy repeater, possible blaster pistol, and possible vibroblade, we're talking one mean mother of a man.
Of course, Canderous actually fought in wars, lead the Mandalorians as a whole, was a bad bounty hunter in his own right, and will flat out take Jango in a melee fight.
The only way Jango can win this is if he outsmarts and outmanuevers Canderous, and with the heavy repeater, the latter option will be harder than it sounds.