IF you are eligible to apply for Brstol's Gateway program (right school and grades in the right bandwidth) then do it.
You stand much more chance of getting an interview for this than the 5 year, because this eligibility criteria will keep the numbers down.
Btw, if you look at the 2019 entry requirements you will see that because the Gateway course wont accept more than a B in Chemistry and the 5 year course wants at least an A in Chemisty, you can't have the grades to apply for both courses.