Adderall - I seem to focus on anything I needed to without resistance, similar to how I would focus on something I enjoy. The side effects on me were (to me) extreme emotional instability, which was too off putting to use regularly - could not play well with others.
Modafinil (and Adrafinil before that) - The concentration assistance is there for when I'm focused, but it doesn't seem to help me stay on topic - I'm still easily distracted. The upside is I can still play well with others, and if anything seem more energetic (I hit the gym every morning I use it). The reduced sleep effect is real, I went from an average of 6 hours a night to <4, and it feels like the regained time is still productive. I have no hard numbers around this, and not really sure how to build a baseline to compare to.
I'd like to see how I react to both together, but hesitant given my poor reaction to Adderall. When I was younger I remember preferring Ritalin over Adderall.
EDIT: Adding to the throwaway comment below, the long halflife of Modafinil is true, especially when trying to sleep. For me, after months of 3-4 days on a week, there seemed to be no long term issues with this, where days I had taken Modafinil I only slept 3-4 hours.
I definitely had issues with alcohol and Modafinil, where at my weight (220lbs) I could normally drink 3-4 pints to reach 'buzzed' status, this seemed to happen at 1-2 pints. This trend stayed consistent - and proper 'drunk' came much quicker. This had the effect of limiting my drinking, to the point where I would switch to light beers and stop drinking after 1-2. This has been positive to me, but a bit concerning as I hadn't read of that effect before.