Holster Retention | Understanding Holster Retention Levels

So I've been carrying concealed for probably 15 years at this point and I've gone through a lot of different holster setups over the years. Started with cheap nylon holsters, moved to kydex, tried leather, tried hybrids, pretty much everything. Each one had pros and cons but none of them were perfect for my situation. I work from home mostly but I take meetings in the city a couple times a week which means I'm on public transit for an hour each way. I also do a fair amount of traveling for work.