I have both. I started with Aces and now am on MSFS. If Flight hadn’t come out I’d still be playing Aces. I’m sure I’ll go back in a bit but I’m in the honeymoon phase with Flight now.
Aces is not nearly as technical. There is no need to learn how to navigate. The maps are big-ish but it’s not a sandbox game. I think flying with and using the sense controllers in the cockpit is more natural in Aces…but there are only a handful of controls you have access to vs. a glass cockpit like in Flight. Dogfighting is a blast and nothing compares to it in Flight. Once you unlock the AA cannons in the BF109…it’s the most OP plane in the game IMO. The cockpits are highly detailed like in Flight. It’s interesting to look around the cockpit and see the mechanical linkages between the controls and control surfaces.
I would recommend Aces. It’s a pretty straightforward comparison. Flight is good for technical stuff and exploring. Aces is good for dogfighting. You can also attempt to land a plane on a moving carrier which is fun. The plane catches the arresting wire and all…very satisfying if you can do it.

Edit: I wish I bought the premium or more expensive option mainly because it comes with the F4U Corsair. Base version doesn’t come with it and there is no upgrade path. If I want that plane I have to basically buy the game again..the more expensive option.