Since you mentioned you play against dwarves a lot, it's worth noting that 1 butcher against dwarves may not tend to get a lot of spells off. You're fielding 4 power dice and 1 bound spell against a base of 4 dispel dice plus 1 per runesmith. Not to say that butchers are no good vs dwarves, but against dwarves and dwarves only you may consider two bruisers as you had listed first.
If you field a butcher, go with the bangstick. If you field a bruiser, I'd not waste points on the spangleshard. Put a siegebreaker on one of them though. You roll weaponskill vs. initiative to hit, so vs. dwarves you pretty much always hit on 3s, and it makes your bruiser's Str an 8, so he wounds basically anything in the game on a 2+, and -5 to the armor save means even dwarves with gromil armor are saving on a 7+.
As a side note, vs. dwarves a slavegiant may not go over too well. He's gonna draw a lot of cannonfire being a large target. They can hit him from anywhere regardless of terrain for the most part, so he'll probably get cut down pretty badly. His main advantage is his terror, but dwarves almost universially have a 9 or better leadership, so it's not worth nearly as much as you'd like. I'd probably consider a slavegiant against dwarves as 175 wasted points that would be better spent on more ironguts or naked bulls to screen with.
It all depends on what your dwarf opponent tends to field. If he goes with lots of mortars or less shooty lists, the slavegiant may work out well. if he never fields a runesmith, a butcher with a bangstick will tend to get off a spell or two here and there. If he fields a lot of cannons and runesmiths, forget about the butchers and giants and just play a heavy-handed army with lots of hard-hitters.
I dont have a lot of experience with elves and chaos myself, so someone else would have to give you some advice there.