well, the argument/question is 'would using solely Marines have made everything run smoother instead of a hodgepodge of SF units'... luckily, since the opposition was a relative handful of Grenadan troops and Cuban helpers, all of our shortcomings weren't fatal to the operation. The one book I have on the operation (written by a British officer, oddly enough) was all in favor of carrying out the operation (the Grenadans were truly suffering under their leadership) but extremely critical in how it was carried out...
Like I wrote earlier the bulk of the problems had to do with the haste. Reducing components changes the time it takes to stand up the assault force, which can help planning. Would be nice to have some in depth research & comparison with beating up Norriegas government in Panama. That had the benefit of contingency plans and a bit more lead time.