I believe the 9mm has slightly more energy, but the old "FBI load" 38 +p 158gr LSWC has satisfied many folks for years. I have 4 Ruger 9mm wheelguns (Sp101, Speed Six, two Blackhawk Convertibles). I like the 9mm for my DA Rugers because the moonclips are easy to load at home then take to the range. Also, 9mm ammo is cheap cheap cheap to practice with. There is plenty of premium JHP 9mm ammo available if you are considering one for carry. I can't overstate the affordability of 9mm ammo. Also, 9mm is very inexpensive. Hope this helped.