Wa alaykum salaam,
These switch offers have a condition that you should deposit a particular amount also into the new bank account. There is a potential that such a requirement causes this offer to be a form of Riba, as it is being given in lieu of a condition that you give the bank a deposit, and deposits are in the ruling of loans. Therefore, it is best to avoid this unless it is from a Shariah compliant bank.
Allah knows best