trust me lone knows his stuff, you dont wanna compare nail gun collections with him
honestly though, the 15 gauge does have more holding power due to the larger shank and larger head, however it leaves a larger nail hole and nails or it cost quite a bit more than 16 gauge nails
i trim out new construction homes and high end reno's all the time and i use a 16 gauge for interior trim (hanging doors, setting window boxes, built in shelving) with no issue. we do have a 15 gauge but its kept for exterior trim purposes when using Azek trim, it requires the extra holding power to hold up against the elements