Do they both fit your magazine? Do they feed and chamber easily? If so, then that is a perfectly good COL.
If you want it to "look good," then seat the bullet deep enough to hide the grease groove. Obivously, if you are going to fill the grease groove with lube, it might be best to have the grease inside the case so it doesn't pick up lint...
I hope that if you load to less than the minimum COL shown in whatever manual you are looking at, that you reduce the max charge weight and work up the load carefully.
For best accuracy, in general, with lead bullets, you want to minimize head space--which puts the bullet at or just short of the lede/rifling.
You sure STI didn't use a 9x21 reamer on your chamber?