A tale of 2 kids:

My older DD (who is borderline MG) was born at the end of October and we (barely) grade skipped her to 1st garde at 5. My youger DD (PG) was born at the end of March and we skipped her to 1st grade at 5 as well. We moved last year to a school district with dedicated gifted program. My older DD is getting by (I even enouraged her to drop from TAG program) but it still does not challenge my my younger DD and we may have to subject accelerate again. (she is asking for it).

I prefer subject acceleration because when they compete in tournaments or talent search, sometimes they enter as their respective grades instead of age. (My PG DD still gets qualifying score for SCAT and EXPLORE even with the grade skip). It is difficult to do subject acceleration in elementary years. (I have seen the successful advocacy in another thread but the odds are not in our favor especially with budget cuts.) If nothing available, I would vote for skip (at least) a grade.