i don't believe the journal overlap amounts to anything when being built in a stock block. any decent crankshaft will be stronger than the block it's being installed in.

the comment about the 470 B being equivilent to the 493 RB is, well, not correct IMO. it always falls back to how you build them and you wouldn't build both of those combo's with the same parts, so how can you even compare them like that?

"usually" the B400 will have stronger main webbing than a RB and that's the only real advantage. bore size isn't really a factor since most factory blocks have so much core shift. i like the RB bearing choices better than the B motor as well as the intake choices. pushrod weight is a total non factor since stronger, heavier pushrods will be used in anything making any real power. the weight on that side of the rocker is almost meaningless anyeway, IMO. the pushrod angles are better with the RB, especially if offet rockers or offset lifters are used.
either engine choice will make enough power to break the block and typically they're within 75-100 horsepower in that regard, but there's no guarantee that either block will safely make X amount of horsepower.