lp dp do more damage so it should be preferred when youre in range.
I use lp dp in those situations:
-Sps, c.hp, (lp) dp, fadc ultra
-c.hp,(lp) dp, fadc, ultra for punishing a whiff move or on block
-c.mp, c.hp, (lp) dp, fadc, ultra for punish
a jump in that you know will connect: jhk,c.hp, (lp) dp, fadc, ultra
If i make a safe jump starting with j.hk, c.lp I am usually in range to confirm with c.hp, (lp) dp, fadc, ultra
I use mp dp in those situations:
-after a cross up j.mk, c.lp I will confirm with c.hp, (mp) dp, fadc, ultra
-after a block string c.lk, c.lp I will confirm with c.hp, (mp) dp, fadc, ultra ( replace c.hp with c.mp for some character)
I also use (mp) dp for a pure srk, fadc ultra frame trap or for anti-airing
This is how I use it, others may have other take on this