Comparison of the base games:
The main difference is, while Queen of the Skies focuses on 1 bomber, Flying Fortress Leader focuses on 1 or more bomber groups/squadrons, so the game play is more abstract.
There are rules for single-bomber play in FFL, but I haven’t gotten to those rules yet.
Each has it’s own mechanic for encounters on the way to the target, and somewhat similar procedures for fighters and flak, and bombing the target. Many of the game mechanics from the other DVG Leader-series games are present in FFL.
Each is fun, in it’s own way. It depends on what one wants out of the game experience, overall command of the mission/campaign, or the results of your own bomber crew during those missions/campaigns.
I’ll probably play a couple more practice missions before embarking on a full campaign.
And I’ll probably try Target for Today before I get to that full campaign.