So first the Quectel EG-25G is a miniPCIe form factor card, we are looking for an M.2 card. The M.2 spec is a little different - smaller and less power consuming.
Then also if you look at other modem please look carefully if they also support voice and if yes, how they do it. Last year when we started doing research there were almost no ready-made M.2 modem cards available that supported voice - but for a phone I guess this is an important feature?
Lastly when you look at bare chips please do not forget that you can not simply 1:1 compare a complete pre-qualified modem module with the bare chips. There is a lot more to go into a modem module than just the silicon parts - like the bespoken qualification, testing and not to forget patent licenses. The 3GPP 4G patents are way over a thousand from several hundred patent holders. A huge amount of money from the modem module price goes into these licenses. The basic rule of thumb is to set aside about 20% of the sales price of a cellular device for patent royalties.
The cellular market is a battle field full of booby traps.