A5 is the best of the 190s. Any one of them flown by an experten makes life difficult for any other bird.
The key is to know the intent of the designer, Kurt Tank. His philosophy was high speed passes, heavy guns that delivered a devastating fire in a short pass, move on. It was designed for boom and zoom. The A8 was the natural progression of this thought, certainly with the 30mm package.
They key is to keep your speed up, with lots of speed in the bank (ie, altitude). Don't turn with anyone, use the WEP thoughtfully. If you get in trouble point your nose down, build up speed and use your roll rate to get the bad guy to overshoot. Also, know the planes you are fighting against. Extreme examples, the A6M5 and 109, both go into compression lock at higher speeds. As they get into compression lock, their ability to roll with you goes to almost nil. Use that against them.
The reason many sticks use the A5 is due to the nature of the MA, where you end up on the deck stall fighting. It outperforms the other 190s, though some like Poison will insist the Ta-152 is the best Butcher Bird in that arena.
The zen of Butcher Bird flying is squad tactics, with 2 or 4 of you. Flown well you will eat everyones lunch.
boo