I really like these, 6€ each is pretty cheap.
However the price is identically for both of them. IMHO the dimmer is better, bc it provides two different buttons, so you can perform two action with it.
Am I missing something? Why should I buy more buttons instead of dimmers?
The only thing I see is usability: You do not have to look closely at the button to perform its action, bc there is only a single one.
Assume you are talking about dimmer and button?
Indeed the dimmer hast 5 actions whereas the button has 3.
At the end it comes down to your preference I guess, as you can program those actions in OH and map them to whatever you like (kind of).
I use both in my home, whereas the dimmers also for now more as on/off switch then dimmer.
pls help me 
What are these 3 or 5 actions? One action is pressing the button (2 buttons on the dimmer, so 2 actions)
I do use the buttons with dresden elektronik’s ConBee II and the according binding.
Have a look at the links provided.
They show, if you scroll down a bit, the different actions.