From experience, priority mail is fast (takes 2-3 weeks) but it seems to get quarantined by custom a lot. The last time I used it, it got quarantined for more than a month before they released it and I've to go and pick it up. But note that I usually only use priority for larger and more expensive items so that might be a factor.

So far I never lose anything shipped Priority compared to First Mail that takes more than a month and I lose 2 parcels and one got stuck at Pos Malaysia Hub for more than 3 months before they care to tell me to pick it up. By then my replacement parcel has long arrived.