SQLIP pool backend - MySQL or PostgreSQL

Hi, I have been using rlm_ippool successfully for more than a year, and didnt have problems with it. Since we have many IP pools(~4-10 per nas) and we need non-continuous IP addresses in pool, I would try SQL based pools. I have read some posts that in MySQL you might get duplicate IPs if you have a lot of connections towards db... Could you share your experience/opinions on sqlip/MySQL or sqlip/PostgreSQL under heavy load, if you use any ? Thanks, Flamur