Veteran's Assault Manual (Blue) or Noble Bright Silver Brooch (White) For Crit Sin?

hi guys,

I'm building a crit sin (first time), currently lvl49, my crit is only 504 (29.30%), final crit is 14%,
I just got a veteran's assault manual (blue) from gacha where is gives +15 str, +15 luk,

should I just use blue set? I'm using a Blue weapon (also won from gacha lvl40),
sins I want to have alot of crit I read that it's better to focus on white equipment? but +15 STR, +15 LUK is soooo tempting....

Thanks in advance