It gets drawn out and takes a long, long, LOOOOOOONG time to finish.
That said, the best version is the a-symmetrical Star Wars Clone Wars Risk.
The reason is that it’s a team game, specifically 2v2. The rep team has the immediate advantage of more land and faster card drawing. The sep team however, has to dig in as long as they can. Once order 66 is called, the sep team rolls a 8 sided dice for each rep territory. The longer the sep players wait, the stronger o66 get. So calling o66 on turn 5 would only make number 1 convert a rep colony - a 1/8 chance. But if the sep players wait 10 turns to call it, numbers 1-7 convert a rep into a sep colony.
Maybe it’s out of line to call it similar to A&A, but if I had to, I’d compare the Axis as the rep and the seps as the Allies. The reps have to strike fast and hard in order to stand a chance. But if the sep players hang on long enough, they will have the advantage, as the US does.
The other Risk variants use the same equality thing that is boring. Imagine if A&A was the same for each force. Difference is what makes it interesting. So if you are going to try a Risk game, I highly suggest you play the Star Wars one. The asymmetry is what also gives A&A its exciting flavor.