The best Service to join as an Officer?

Hello. I would like to join the Forces as an officer, but I would like to make most of it. I would like to get to know which Service is more prospective in terms of career. I would like to be a General/Marshall/Admiral one day so it is very important for me to make a right choice. I have got a BA Criminology 2.1 degree and now I'm 27 (nearly 28 YO) and currently working for Civil Service.
So I can not join Royal Marines or RAF as a pilot due to my age. I believe the pilot or engineer officer is the best career for RAF, but I'm too old and don't have an engineering degree as well.
So I'm thinking about warfare officer career in Royal Navy or some platoon commander in Army. Apparently there are more chances to reach highest officers' ranks in the Army if you are an Infantry or Armour Corps officer. But I am not sure that I will be a good in Infantry. So I was thinking about Royal Artillery or Royal Military Police (but there are no Generals in the RMP!). Also I am considering RLC or AGC as plan B or plan C, D, E, etc. But the Royal Military Academy Sandhurst training is the longest (44 weeks), meanwhile Britannia Royal Naval College (BRNC) course is 30 weeks, and the Royal Air Force College Cranwell is just 24 weeks.
So can You give me an advice on that.

By the way, did you resolve the issues you mentioned in this thread: https://www.thestudentroom.co.uk/showthread.php?p=79458154&highlight=

Because if not, it doesn't matter what that vote says, you're not getting in.

Sorted. I am just thinking now on what service to join.

Sorted. I am just thinking now on what service to join.

Based on the highest rank you want to reach and the length of officer training???

Radical suggestion, but what about a role in which you have an actual interest? After all, you're more likely to be doing that for years than being a staff officer.