Hey @cmm - I would argue that a nucleus is always the better option as you pay for already drawn brood frames with brood, honey and pollen stores, whereas the package is just bees. However, perhaps there is a higher risk for the spread of disease with a nuc. Always buy from a trusted seller.
This previous forum post may offer some more insight too - Sourcing bees: Nuc/package/split - what's the difference?