Better to have something than nothing, as long as you know the limitations of your choice, be it caliber or gun. Those that know me, know I'm not a fan of mouse guns or sub calibers, but a guy I hold high respect for, once said "10 good hits with a 22 are better than a bad hit with a 45", and I had to agree.
I may not agree with your choice of gun or of caliber, but it is your choice, I don't have to carry it, and you'll have to live with your decision. Just as I'll have to live with mine.
Just understand the limitations of your gear, and train, train, and train with it, get as proficient as you can, with what you chose.