To be fair, the difference between them is the fact of money and talent. Villa is there not because they spent much money, they are there because they have Unai Emery, one of the best managers in the world and this is why they are trying to be fourth, and will probably achieve it as well.
However, we need to also remember the money part which Chelsea has a lot of and because of this reason they are doing fine as well.
When you spend this much money on a team, you have a good depth, and you have some good players, money does play a big role in football these days, while Chelsea won't win the league or something, they do look alright and I believe they are going to fight for that fourth place but will end up fifth if you ask me.
This isn't really that bad in the end because it allows the player to go to Europe once again and try to do the best. As long as they are in the top five that is not a bad result, they are a young team with some chaos, they will get better with time.
Chelsea and Aston Villa shared the same points on the EPL table but the Blues tops them with goal difference. Chelsea have a pattern to win matches with solid game plan by Enzo Maresca and with him, I trust Chelsea to end up top four this season. While Aston Villa having Unai Emery, one of the most effective coach in England, he's acquainted with the fact that elite clubs doesn't scare him, always hang in the balance to exert more meaningful results for his team. Looking at their performance, these clubs have upgraded to be better versions and we know how desperate they're for accumulating points this season. There'd actually one thing for sure, Chelsea and Aston Villa are not title contenders, they just aim at ending top four this season, it's quite open and straight for everyone to understand this scenario.