Branches of tradeskills (Gnomish eng., etc)Follow

Hey all,

Had a question about what appears to be different "branches" of tradeskills, like tribal leatherworking and gnomish engineering.

How does this work, when do you choose which path you will take? Is it reversible, can you choose both, or only one?

In my case, I am wondering what kind of Engineering to go, goblin or gnomish.. what kind of stuff can I make with either of these that would help, mostly in PvP. I know that the gnomish death ray and gnomish mind control cap are "gnomish" because its in the name.. that sounds kinda cool.

Also wondering which way I should go with my leatherworking huhnter when he gets up there.

My main questions are:

How do you choose which path you go in?
Is it reversible, or can you learn both?
What type of enginnering will help my team and myself out in BGs? (Im a warrior on this toon)
Thanks all.

Just an FYI, tailoring and alchemy will have specializations in TBC.

http://www.curse-gaming.com/en/general-news/184/2-0-3-unofficial-beta-patch-notes/

I also heard people talk about the possibility to switch subprofession in TBC without having to redo the profession all over. Can't confirm this, as I don't have the Beta myself. This won't be as usefull as it sounds, since in TBC, most of the endgame items you can make, also require the profession to use it. So say you're an armorsmith and made yourself some epic TBC items, then when you discard armorsmith, you can no longer wear those items.