Would deffo go with RAF like if you're going into aviation, better kit, equipment, 5 star hotels on exercise etc [emoji6]
Ive just left the army as an aircraft mechanic, no 5 star hotels for us! Not too sure what it's like in the RN but I almost had to get picked up from Cyprus whilst I was on exercise to go to Libya, the lads who originally deployed from 3 Regt AAC hated it on ship. Can't fault you for following family footsteps though. If you do join RN then you'll have to volunteer for the field gun competitions, the army put a team in every year from 7Bn AAC I took part back in 2012, the navy tries to make up every excuse for us not to win [emoji13] one of the best things I done in my career.
But yeah they are having a massive recruitment drive, I've just had a letter through offering 15grand to join back up.
They used to turn many people down at selection for random stuff like heart murmurs, when they never had history of them and then after seeing a specialist there was nothing wrong. During such a big recruitment drive though I doubt they'll be less picky.
Good luck