The older, DOS version of the game is better in my opinion. A LOT more targets and the enemy fighters will attack you all the way to and from a target (MOST of the times, you were intercepted twice by 4 planes each time you crossed an airfield's defensive circle. Once when you entered then again when you were leaving). The down side is, I've NEVER seen a 109 in it, but plenty of 190's, 110's and rarely, 262's. You couldn't choose which targets to hit, no escorting fighters and you were the ONLY bomber in the formation doing any shooting.
The newer version allows you to play as a squadron commander and choose targets and manage the squadron. You also have little friends, ALL bombers shoot at stuff and the eye candy is much better than the older version. You can also fly any plane that is up, including the interceptors. Down side is, far fewer targets and the enemy fighters will only attack you 2-4 times, after which the only thing that will keep you "company" is the flak for the rest of the mission.
BOTH games, if you zoomed in far enough on your target, you'll hear air raid sirens.
While I was disappointed by the down sides of the newer version, it's still fun to play. I really like the ability to choose my targets as well.
