I thought ventral points would be able to carry heavier loads.
IIRC I heard Shi Lao and Yankee mentioning that PLAAF prefers big calibre PGMs for assured kills. But at the same time, they are using dumb 250kg. It's perplexing.
The US pays $4K for a 250kg class dumb bomb. Then I see an Air Force JDAM kit starting at $21K. That comes to $25K in total.
So given the large increase in cost for a JDAM kit, you might as well go with a larger 500kg bomb to guarantee the target is hit. So the total cost goes from $25K to around $29K.
The JDAM specs are around [4m for Laser guidance] or [13m for GPS+INS] or [30m for INS only]
If you assume that GPS will be jammed or laser targeting is not available (due to clouds), then it would make sense to go with a bigger bomb to compensate.
Of course, the drawback is that less bombs are carried per aircraft sortie.
This applies to gravity bombs without glide wing kits.
But if we're talking about glide bombs, the weight of the bomb does impact the standoff glide range.