Liverpool getting out of the Champions League may be advantageous to them, but they shouldn't have left so quick when they have already given much effort from the beginning only to fall out along the line. Besides they were still topping the Premier League table before they fell out of the Champions League games but anyways, since they will be concentrating more in their Premier League games, it will give them an edge to draw closer to the title glory and it is becoming a reality for them already due to the point gap they are topping with.
Arsenal is not to be trusted in the Champions League because they almost put in same efforts as Liverpool did, except they will prove that they are prepared this time around if not it has always been same story for them whenever they appear in the Champions League so until they make improvements, they can't be hoped on to do anything in the Champions League games, Moreover there are still teams that are stronger than Arsenal so it will be difficult for them to scale through.
Aston Villa have been so loose this season in the Premier League but since they have also given some good display in the Champions League and got to the level they are now, they have also tried their best and even if they don't advance further, they have at least gotten the Champions League experience. There is a strong challenge in the 5th position in the EPL which means that Aston Villa may not have the privilege to reach the 5th position and qualify for the Champions League next season.
Regarding Aston Villa in the Champions League, yes they have really tried because even I didn't think they can get up to this stage of the competition, but the truth is, this particular stage might choke them but hey this is also football where anything can happen at any point in time. Liverpool didn't leave the competition at their own accord, they were eliminated and I see no advantage on them leaving at this stage, because it now this period that they were supposed to concentrate on the competition since they are 13 points ahead of Arsenal in the league with less than 10 games to go.
Aston Villa surviving up to this stage is surprising, they haven't been the best team in the Premier League but are able to remain till now in the Quarter final of the Champions League. This will be the challenging part for them, and we can't possibly tell the chances of them shooting past this opponent, the team that eliminated the long leading Premier League contender, PSG is a well placed obstacle, it should be them making the heat and still qualifying for the Semi finals.
Aston Villa has nothing to worry if they get eliminated from here, it was a good season on their, lot's of big clubs has been eliminated but they still remain, practically they have no chances of playing in the next Champions League because every position has been sealed, they are not remarkable in the Premier League that should have qualified them.