I think there is no doubt that the feeling of flight and the beautiful rendered cockpits in RoF hold the edge at the moment..
But it's good to have choices, last night for instance I played two career missions in RoF, then jumped into OFF for a go at my career there as well.

Each sim has it's advantages to be sure and I appreciate the strengths of both. The reality is that the flight sim market is a small niche' market and the WWI flight sim market is a small subset of that, with most flight simmers being into WWII or modern day jets. Because of that, it's really a small miracle that we have any choices at all considering how time consuming and expensive they are to produce and support, not to mention how picky we flight simmers can be.

Hellshade

As prices were very reasonable, I recently bought OFF + Hat in the Ring extension.
With all the sounds, FM and DM mods, I enjoy also flying it. It has other planes, mainly in the early war times (FE2b, 1 1/2 Strutter, Halberstadt DII, Roland CI ... ) I like the historical accuracy that goes in the campaign. If you raise the difficulty settings it is interesting and as I started flying sims at 640 x 480 VGA, I easily forget the graphics look a little outdated.

The main problem for me is the same as RoF solo : the AI planes. Your wingmen are specially stupid and can't follow you even when you change course they turn a mile away and take 5 mins to be back in formation and enemy planes are too easy to shoot down. ( although with reduced gun accuracy in the settings a tad more difficult than RoF )
I confess I am a lousy fighter pilot ( fly more often 2 seaters ) but if I look at my solo career stats (both RoF career / Pat Wilson CG and OFF) 90% of my pilots "end of life" are due to spins, collisions or Flak. The few times I've been downed by AI planes were bad attacks on two seaters at the time the rear gunners would snipe you from 300m...

This is why I spend most of my flying time on MP servers, even if I get my butt handed to me a lot more often than I would like...lol
But when flying scouts I don't look anymore for kill stats, but rather to survive like any real pilot of the time would do, so I am very careful in picking up my fights, don't hesitate to run away and come back later when necessary, and try to team up with other planes or fly escort missions. Last night was a good example, 2 hours flying, one successful bombing mission, one successful escort mission, defense over the lines, 3 kills and no death ( had to make two dead stick landings )

The very best of course is for me to be a squadron member and fly coop missions with your mates against other squadrons.

They definitely have their pros and cons, OFF's ground war is fantastic and it allows more customization of the experience and more AI in the missions.