Unfortunately, I have no idea
Eh, but then worth it? Skeptical about that, but oh well.
Any news on when it's going to happen yet? I've been looking forward to it for some time now.
Scroll down a bit to the changes they're going to make regarding mythical units.
Erinyes: More attack power, higher resource cost, lower favour cost (480 -> 330)
Manticores: More attack power, higher resource cost, lower favour cost (405 -> 270)
Harpies: More attack power, higher resource cost, lower favour cost (130 -> 85)
Cyclops: More attack power, higher resource cost, lower favour cost (360 -> 240)
They also are taking down a few values, the defensive value of medusae's for example. However, the majority of the changes will encourage players to build more mythical units, and it definitely will be worth building them: most of the units will be better than they already are.
Even though there is no set date for these changes to be implemented, I think it will be before the end of 2013. I'd like to emphasize the line "I think" - I'm not a dev, nor have I contact with any of those, so I can't give you anything solid. I base this on the way they say they're rounding things up.
As for the topic: I myself prefer to start of with Hera, especially with the new Quest Line they implemented at the start of a server, it's a huge benefit to use Hera to your advantage. When I found my 2nd city, I usually go with what the farming villages are willing to offer; if they offer stone for wood and silver for wood, I'll stick with Poseidon, and trade the resources I get from Kingly Gift for silver and/or stone.
If it comes to my favourite deity, it would be Zeus, for offering one of the best units in the game, the Manticore - ignores biremes, has high sharp offense value, is fast, and can carry a reasonable ammount of resources. Anyone that doesn't love this unit, should start doing so!