A dana 44 and the warn hub kit (where the spindle comment came from) use the same bearings. Being that the are the exact same bearing, they are far from about twice the size.
But.. the hub kit spindles are chromoly, and better designed than standard dana 44 stuff. A broken stub on a warn hub kit won't swell a spindle the way a dana 44 does.
That broken stub is less likely too, because the warn 30 spline shafts are considerably stronger than 19 spline dana 44 stuff.
3 bolt vs 6 bolt spindles is also a non issue, since both spindles are hubcentric and not supported by the bolts. They are just there to stop the spindle from falling off.
And yes, if you want to go to 8 lug and 16.5/17" wheels, you CAN get dual piston calipers on the ford dana 44 stuff, but then you're talking about new wheels, new 8 lug rear end, slippery slope.