If you only log in once a day you'll get more energy from a refill 2 x 100 assuming those are your only options. As soon as you log in twice a day, more than an hour and forty minutes apart, you'll get more e from a dp.
As above though you should aim for both, as well as a host of other things.
If you had compared DP vs 3 Xanax a day, I could maybe see a potential debate for either side..
However DP against daily point refill doesn't even come close.. A DP gives 720e daily whereas without donator status, you would just have 480.. Difference of 240e per day..
Points refill, without donator status is just 100e daily.. The comparison doesn't even comes close..
That said, an even better way is to use both a DP and daily point refill after..
On "minimum daily hours of activity", it's not how many hours. You don't have to play hours a day to be effective.
What works the best is checking in multiple times a day, for just a few minutes each time.
If you play for 2 hours every morning, and don't log in the rest of the day, that will not be nearly as effective as if you put in 10 minutes each time you log in, and log in 5 times a day, every 4 hours except for an 8 hour break while you sleep.