How are earmarks and pork belly spending different?

This needs a little further refinement but here's my first take on it:

Earmark spending is spending based on pre-decided budgets; for example if a school got 1 Million of spending the previous year then it deserves the same (at least) this year. This many a times creates wasteful spending as its allotted money which may not be required the current year and may be it was required the previous due to say additional construction of tennis courts on campus.

I think what you are referring to pork belly spending is really pork barrel spending in political lingo, if so what it means is spending money in ones own constituency to gain popularity within the constituents. Generally senators allege each other of this, generally and specifically during presidential debates as was done during Obama & McCain debates. The argument goes to say you are only good for your own territory and not necessarily the nation which the president should be, at least that is the expectation from rest of the country.

As ever

Ash