May I know how long have you been in your current role? I would think 5% is too low. The reason you are offered means they are willing to let you take on the role. Just that I am not sure why is it just 5%. Personally I won't accept this offer even if the exposure is bettter or responsibilities are wider. You won't know until you start the new role.

You are better offer staying in your current role while looking other opportunities.