What's the difference between stake and deleguate on the elrond wallet? Which one is the best?

Delegate stands for Legacy Delegation which is the delegation towards Elrond Foundation’s nodes. It is similar to the delegation on the Staking Pools’ nodes but it has few differences. In order to reach into the Legacy Delegation Pool or as the community calls it, active delegation, you have to go through a waiting list which works on a first come, first served basis. The minimum amount that can be delegated is 10 EGLD. Another difference is that Legacy Delegation Pool does not allow rewards restaking.

I would say to stake with Maiar wallet app for flexibility

It doesn't matter as long as you are staking ?⚡