I have to say, Lock On does feel more realistic (despite having no experience flying modern jet fighters or vintage warbirds!). You can't just power up, take off, open fire and get an easy kill like you can in CFS3. If you tried that, you'd either give up trying to figure out what the hell you had to do, or stall and crash after your first sharp turn.

Although CFS3 is fun, I think that Lock On is more immersive, and you get a greater feel of actually being a combat pilot, due to the level of work that you have to put in. Hard? Yes. Fun? Most definitely.