I think a tapered shape, smaller at the top and thickest at the base, is better.
First of all, it makes initial penetration easier. You can do shallow strokes to loosen her up and then give her the big girth later. With a baseball bat she needs to be totally ready before any action. Second, blow jobs are easier. Third, it is easier to avoid the cervix with a tapered shape.
I have a bit of a baseball bat going: 5.75” mid-section, 6” below glans, and 6.25” glans. It takes a lot of foreplay before I can get it in. If I start with a tapered dildo, however, I can get them ready much faster.