im yet to test, but i belive one +10 weapon with anti elemental cards + endow does more dmg than one +7 (yes, smiths barely take elemental weapons to +10 since it gets expensive) elemental sword
for example. lets suppose you want to kill kasas (i only use this example because their cards are easy to remember

and giving a pike example) one +10 [Peco egg*2][vadon*2] pike + water endow should do more dmg than one +7 water pike or any other spear type weapon. however just a theory and requires testing to be 100% sure
ok, using doddler calculators this is what i got.
using one 99/70 LK with 99 str, 99 dex and 25 vit (not the best stats but wtv, just to ensure the dmg and hit) with spear mastery and on a peco
with elemental cards + endow these were the results
Minimum Damage 816
Average Damage 824
Maximum Damage 832
dmg with spiral pierce
Minimum Damage 3050(610X5hit)
Average Damage 3050(610X5hit)
Maximum Damage 3050(610X5hit)
if pike is +10
Minimum Damage 856
Average Damage 864
Maximum Damage872
same SP dmg since its the exact same weight/upping
if pike is +7
Minimum Damage 840
Average Damage 840
Maximum Damage 840
sp dmg
Minimum Damage 2990(598X5hit)
Average Damage 2990(598X5hit)
Maximum Damage 2990(598X5hit)
source :
http://rode.doddlercon.com/db/calc/seems ranked WS +7 VVS water pikes win on this one with +16 (average) dmg even if just +7