What is it like to go Infantry in the Army as a prior service Marine?

You should feel right at home. Infantry units, and Army Combat Arms units in General, generally have that same style of discipline and esprit that you find in the Marines. What you will find different is the supply situation where gear is readily available and that the promotion rate in the Infantry tends to be pretty fast if you get your schools and go your job. You will have to get used to calling all NCO's sergeant, which I disagree with BTW (Marine Corp way is better).

I know a lot of army infantry offices being a QM warrant. Best thing about the Army INF is the promotions are quicker.

When I came back in, the Army was looking for 11X. See if your recruiter can pull 11B/C/X for you. Take a look at the Army business rules too if the MOS isn’t opened.