Boss dmg 20% or ma+70 ?

which should i choose ?

let say i have a Staff ma 304 [Element Staff] [Speed Fast]
and a Lv150 Staff with ma 374 [Speed Slow]

for BaM , which should i choose ?
my azwan inner ability is boss dmg 20%

if choose slow staff , i will give up the 20% boss dmg. and swith to attck spd +1


for future pt member , i have:-

BaM
Paladin
DemonSlayer
Bishop
Beast Tamer [haven come yet]
Kanna [Mule] [for boss dmg buff]

since beast tamer have a random pt skill is + attack spd , but the chace to get is random , so

pls help me , which staff should i choose [our server too far for farnir weapon, so i dont have think too far]

pls help