"While we don’t know when they’ll be released, both will contest Moltres as the greatest Fire-type DPS. In the current Game Master, Ho-Oh isn’t much of a threat having relatively poor movesets despite its gargantuan CP. Entei has a slightly lower attack stat, but is bulkier, doesn’t have a Flying sub-typing, and has access to Flamethrower (where Moltres is currently limited to single bar charge moves). If you’re in a hurry to get a good Fire-type or are stoked about Moltres in general, we at GamePress believe it is a safe investment, despite future competition."
https://pokemongo.gamepress.gg/countering-legendary-birds-and-their-place-meta
NB Moltres has 'flying' typing which adds a difference between it and Entei