The two are completely different worlds when it comes to multiplayer, and it's a lot easier to reach a higher rank in 2v2s since you have friend to coordinate with and dump admiral skills, or make fleets that complement each other so much so that they're borderline unbeatable.
Chaos is probably the most unsatisfying faction to play right now. The dps is abysmal so it take SOOO long to kill things. I just got out of a game against a tyranid where i spent upwards of around 10 minutes of constantly kiting his ships while my carnages did painfully slow dps. I just got so bored of the game i let him catch up to me to brawl and i ended up losing anyway even though i had the advantage of 10 minutes of constant fire on him.
Asuryani are the strongest faction at the moment. Especially against large ships like your despoiler. They get 8 torpedoes each on their standard 200 point cruiser. He definitely just point-blank shot you with like 24 torpedoes and scrapped your ships in 1 or two runs. There's not a lot you can do against them right now.
I think the CWE cruisers should be nerfed from 8 to 4 torpedoes per ship. It's ridiculous that ships with that much armor and speed should get the cheapest torpedoes in game. The speed and maneuverability of eldar ships already make landing torpedo shots incredibly easy, they don't need 8 of them. Imagine an Imperial Retribution battleship with the speed and maneuverability of of an eldar ship with vauls maneuver all at the cost of only 200 points. That's what CWE is right now.
Tau is probably the easiest faction to play besides tyranids. You literally just click on the ships you want destroyed and watch your fleet shoot it to death. Once in a while you may want to send off some fighters or homing missiles. Besides that just keep your flagship alive or else everyone will mutiny quick. That's literally all there is to tau.