Are they safety (probably) like bitcoin qt?
Slightly less safe, but safe enough for use by most people.
What is the main reason when you choose a wallet?
That's like asking "What is the main reason when you choose a vehicle?" There are many reasons, and each person will have their own criteria.
Each wallet has their own interface and their own way of handling security. Each wallet has it's own "quirks" as well. You should probably take some time to learn about how each one operates, and then decide which will best suit your needs.