Dual Wield magnus output damage and crit rate are from average to good,SMs can do way better.
Both 1h and 2h are good,but you'll have to compensate on both,2H = You need def and HP 1H = You need STR or damage output in crit
The only good suggestion is. ALWAYS AXE unless you really need a lot of def,sword doesn't seem like a good idea at all for magnus
1H has 2 4 second stuns,and a poison,including Sonic Boom and D.Sonic Blast
2H has a total of 3 Stuns,including an AOE one,and a great critical rate