Which MOS within the intelligence community would set me up with the best options post-military?

It would be better if you focused on the career field and your duty for the country.

That depends on what you want to do post-military in those organizations, because they are different. And, even within those agencies, there are also different jobs. Do you want to be an investigator? An analyst? An intelligence collector? An intepreter? Your question can be answered more easily if you let us know what exactly it is you want to do.

1) Instead of focusing on how a MOS will benefit you, you should focus on how you are going to benefit that MOS and the peers you’ll have to your left and right and the personnel on the ground you’ll be supporting...
2) Having the job doesn’t help get you into a career outside the military. It’s the education that you obtain and the experience and time in the job that gets you looked at for the civilian job. No matter what the job is (Especially in the Intel World)
3) As a possible recruit, I wouldn’t be worried at all about what is going to get you the good job outside the military, I’d worry about researching what is entailed of you to even graduate the AIT to be MOS Qualified. (People join the Army and look at the name of the job and don’t research the job and either wash out in AIT or get “pushed” through AIT and then go to a unit that supports real life missions and don’t know how to do their job, because they picked a job that sounds cool and end up in over their head.)

Do your research. But to answer your question: As a person that has any Intelligence Background (No matter the specific subject) with experience usually 3+ years some more you are opened up to many jobs in the Alphabet Soup career field.

Honestly the intelligence field is extremely specialized into over 20 different disciplines and hundreds sub-disciplines. Like Jade and Braden said it depends on what you want to do.

Frankly you want a easy slot into the FBI become a financial tech because you get experience in accounting and following money.

35M gets you into CIA, FBI, field agent. You can do analysis with HUMINT too, so it’s more valuable in my opinion. You’re an interrogator, collector(agent if you go CI), and you do analysis, so unlike a 35F that’s just an analyst you have that plus more.

As it's been stated below, it entirely depends on what you want to do post military service. Being a 35F will give you a more general overview of the more technical disciplines while training you to piece several pieces of the puzzle together to make analytic judgments. 35N/S/M will teach you very technical skills in their respective areas that you can transition to various three letter agencies or contracting. 35P's will teach you a language that you are deemed qualified to learn, as well as more technical aspects.

The other side to that is the promotion system. If you choose to stay in and make the military a career, different MOS's promote at different rates. For example, I am a 35N and have promoted much faster than my Spanish speaking 35P comrades.

I’m currently in AIT for 35M, so I obviously don’t know much about the post military options or other MOS’. However, from what I’ve been told while training, it seems as if 35P has some great options for careers in the civilian sector.

All intelligence MOS’ will have their own benefits, because they’re all great jobs with clearances and cool training. I’ve been told 35P is a slower desk job, 35L seems to be very interesting, and I’d probably choose that if I were to have to change my MOS. But so far, I’ve experienced very cool training as a 35M, and it seems like it’s going to be a very fun job.

Just choose whatever MOS best suits you. 35P is a very mentally challenging MOS, while 35M requires you to have good social skills. Just research each intel MOS and decide which one fits your personality best, because at the end of the day they all offer great options for the civilian sector.

Get in and do your duties and take your future plans a step at a time.
Don’t need some guy with his head stuck in the clouds before he even gets in.
Baby steps !

It depends on what you desire to do within those organizations. They have two very different missions.

What are your interests?

Just load the wagon, and don't worry about the mule going blind. Rather than focus on being a driver, and later finding out you were better as a loader.