Firstly well done on getting two job offers.
My advice without question is take the second one.
Reasons:
1 - AP is AP whether it's in a FTSE 100 or SME. Don't take a job today in the expectation of getting a fantastic promoton in a year. It may happen but often doesn't.
2 - Second role may also invole AP (?) but also covers year end, payroll etc and some Non Finance exposure, dressed up we call that commercial experience and great to put on the CV. A chance to do quite a broad role. if the company is growing you may find your role grows too and you gain far more variety of experience. Always be prepared to take on more in these kind of roles as it shows you are keen and you can get the opportunity to get some quite good experience.
All the best
