Paying for Hammer means paying for losing an attack. Both dual-fists and fist+sword gives +1 attack for 2
CCW. Hammer doesn't. Every option is S10 with AP2. Though technically you could make the attacks with sword instead of doomfists if you wished to use S6 instead of S10 for some reason.
Anyway, Admiral Ackbar already stated his opinion about thunder hammer: It's a trap.