We are in the Process of installing a new Septic Tank and wanted
people's opinions on if I should have a 3" line to the Tank or a 4"
line to the tank?

I would use 4" from the house to the tank, 3" for main lines inside the
house. Remember to put a cleanout tee near the outside of the foundation
for easy maintenance in the future.

3" is supposed to work better with today's low flow toilets, as a 4" pipe
lets the smaller amount of water spread out too thin to carry the solids
away. Of course, anything that does get left behind usually gets washed
away with the next flush, laundry, shower, or sink usage...

So it seems like there are plusses and minuses to both. I'm going
about 80' from the house to the tank and have the 1/4" drop that I
would need for 4"

1/4" per foot is about the ideal slope regardless of pipe size. But, you
can get by with 1/8" per foot on larger pipe if you have longer distances
to cover.

1/4" per foot would require about a 20 inch drop over your 80 feet.

1/8" per foot would only need about a 10 inch drop for the same 80 feet.

I'd still choose the 1/4" per foot slope if you have the height to
accomodate it.

Anthony