If it were me, I'd go with the 38 Super. It's a "known quantity". Very reliable, plenty of power, excellent accuracy, and available. If it were a "fun gun" for the range, a 9x23 would be an interesting choice. For self defense, I wouldn't even consider a "non-standard" round. Maybe there is a good reason why it isn't offered by popular manufacturers. Usually when a cartridge gets good reviews for power, accuracy, and function, many manufacturers will jump on the band wagon and start making them. No so with the 9x23.