Which is safer to take..150mg ranitidine or 20mg omeprazole?

Both are very safe: Omeprazole is on average more effective overall, and sustains the effectiveness over the long term. If you are happy on ranitidine, there is no reason to change. Omeprazole has been associated with osteoporosis, and certain antibiotic associated diarrheas, and other rare side effects. As drugs go, it is very safe and very few people have problems with it.