In the end it`s about the kind of sound you want to make and how you would want to improve it. A neck strap is handy for times when you are playing standing (as you obviously can`t glue a chair to your butt and still use a seat strap!). Unfotunately a neck strap or any other strap that holds the most of the weight of the instrument on your shoulders and upper body will exert strain in those areas.
It`s very difficult to produce a very open clear sound with no stress if your neck is holding the weight of the instrument.
I had been using a bass clarinet harness that spreads the weight around my back and found that better than a neck strap but my playing is now entirely with a seat strap. This was on advise from many pro bassoonists. It can cause some discomfort in the left hand as you are using this to support the weight more but as you have freed your upper body and hence lungs, your tone should open up once you become used to the seat strap. An alternative is a spike which comes out of the butt joint of the bassoon and fixes into the floor much like a cello spike.

when i started playing bassoon my teacher didn`t say anything. the school bassoon had a, what i found out later, seat strap and i have no idea how to use it. if i just sit on it and hook it up, the bocal pokes me in the chest... is it the bassoon?

Seat strap, neck straps are painful. End of story.

I prefer a neckstrap, it`s much easier to adjust.

Seat strap all the way for me. The dodgy old bassoon that I use had a hooky thing for the neckstrap, but as soon as I let go of the bassoon to play, it came out.