I agree with what has been said by the more experience and that the Tamurkhan is most wildly accepted. And what your gaming group accepts. Whatever you use will, though, be dictated by a tourny you join in on. Two points I’d like to add; ed 8 of the warhammer rules , in the first few pages, states that the rules are a guide. Also the LoA is just one legion of chaos dwarfs of many and it is specilized for where it is from Azgorh. There are other legions that may include bolt throwers and slaves and for these, also, there are recent rules… :hat off
Forge World’s stance has been that the Legion of Azgorh is its own list and it was never intended to replace any existing GW army list - so in that sense the Ravening Hordes list could be argued to still be vaild.
That being said, however, there’s been very little talk about the RH list since LoA came out and I haven’t heard of any tournaments that have allowed it… plus it’d be too confusing for other players that aren’t familiar with Chaos Dwarfs in the first place, as they’d need to know about how two different army lists operate for a rarely-encountered army.
The thing is, Tamurkhan essentially has all the units Ravening Hordes does (with the exception of the greenskin elements) so there’s very little point playing the older list. You can quite easily just leave out the K’daai and other new stuff and have a functionally identical force. So just stick with the new rules.
You gotta consider where and who you’ll be playing. Yes LoA (aka tamurkhan) is "officially accepted most places, and it has some lovely machines etc. But it has its low points and detracters in certain cases.
You’ll probably be facing updated armies and RH is way outclassed.
I thinking Thommy’s book is the way to go if everyone you face is friendly