Warfarin (i.e. 'Ratsack') poisoning is horrible - it causes the poor animal to bleed to death internally. Not quick, not painless.
Snap traps are probably worse - they often don't kill outright & the unfortunate mouse suffers for hours - or will chew off a trapped limb.
There are humane alternatives:
https://www.ebay.com.au/p/?iid=26258...hn=ps&&&chn=ps
Dean