I think both have their merits and i voted accordingly, despite the fact that i'm a primarily offline flier.
I did use to rack up a few weeks of online flying every few months with the previous series and i liked it because it's a different set of challenges.
It's still early days but the fact that it's possible to plug programming language code straight into the sim bodes very well for the future, to the point that i suspect we could some day have a dynamic campaign engine working both offline and online. Heck, if i knew how to properly code in C# i'd probably be working on a campaign module right now.
This would be good enough to get me to fly MP more, because the main reason people do unrealistic things in MP is that they don't have a suitable framework that demands realistic gameplay from the players. If exaggerated gameplay styles carried a relevant and realistically accurate penalty in MP, then at least the people flying in high difficulty servers would also fly in a more realistic manner.
For example, if bombing the factories and attacking supply convoys, trains and vehicles meant that my base would be low on fuel, spare parts and ammo to the point that i'd have to be taking off with reduced load-outs that limited my effectiveness, then i'd be more inclined to fly a proper CAP than head for the nearest mid-channel furball.
I would take care of my aircraft and try not to take unnecessary risks, because ending the mission would place my aircraft back into the airfield's pool of available airframes and if it was damaged it would be moved to the maintenance hangar and be unavailable until supplies came in and repairs carried out, limiting the amount of aircraft my team could fly from that airfield.
I would properly support my teammates in bombers because their success would mean benefits for me in the long run, eg fighting against 109s that have to take off with reduced fuel loads, etc etc.
I did do these things in IL2 as well but that was just a personal gameplay choice of me and certain like minded players because there was no long term goal, usually the longest running missions on most DF servers lasted 3 hours or so. In most cases on the same server you would see half the people dogfighting just for fun and the other half actively going after mission objectives in an organized manner.
Coops were more structured but had their own drawbacks because it was a very rigid and unflexible situation, limiting the players to flying a certain mission without the possibility of improvising on the spot or carrying out ad-hoc sorties they would think up themselves to achieve objectives in a more efficient manner.
Now that both MP modes have been merged into one it's possible to have the flexibility of DF with the AI support of Coop in one mode and with the scripting tools and how the engine works it's very possible to have official and 3rd party campaign modules as a separate layer on top of the base sim, providing us with what's needed to fly with consequences that will have a tangible and often immediate impact on what we're able to do on each sortie.
Now there's really nothing wrong dogfighting for the heck of it, it's just not everyone's favorite gameplay style, some people prefer having a sense of purpose behind the fighting itself and that's where the structured environment comes in.
For example, i'm a terrible dogfighter so i avoid dogfights and this results in me remaining a terrible dogfighter
However, i'm a more or less good to above average marksman that can get comfortable with certain aircraft armaments with a bit of practice and pull off good snapshots, i'm an ok tactician which means i will usually score less kills by avoiding dangerous situations but i'll also die less and for CoD in particular, i have a relatively sound understanding of aircraft operating principles which lets me squeeze a bit of extra performance out of my aircraft.
For me to be able to employ what i'm good at in MP, i have to fly in a way that doesn't focus on getting a steady tracking shot from someone's six. Having an environment that rewards each player for using his strong points would massively improve gameplay and the overall level of competition by introducing more variables into the mix.
For this to happen though we must move along the path that the sim's engine itself has carved, merging both MP modes and then using the same underlying architecture for SP, or in Luthier's words "SP in CoD is like flying MP with a single human player in a server full of AI, the code behind it is the same in both cases".
That's why i voted for both, because it seems that they're actually interwoven to the point that it wouldn't make sense to split them up at this point in development.