Well, what S-E has confirmed in interviews is that you get to pick your starting city, and it is not like FFXI where certain races were "traditionally" from one city or the other (like Elvaans got a ring if they started in San d'Oria). They've also said that while certain job classes will have their HQ in various cities, there is some overlap. Like for instance they have said that there is a Fishing Guild in Limsa-Lominsa as well as in Gridania.
As far as how the HQ will effect your advancement in that class, your guess is as good as mine. :/
Pure speculation: Based on S-E's emphasis on everyone being able to do whatever they want, I think the HQs are not necessarily going to be like, the place you go to every time you level, but maybe like the place you go to for class-specific missions or quests. That is my guess though.
As far as how the HQ will effect your advancement in that class, your guess is as good as mine. :/
Pure speculation: Based on S-E's emphasis on everyone being able to do whatever they want, I think the HQs are not necessarily going to be like, the place you go to every time you level, but maybe like the place you go to for class-specific missions or quests. That is my guess though.
http://www.tale-ffxiv.com
The Adventure League of Eorzea: A progression & RP guild. FFXIV's longest-running RPLS