I’ve been using a TG-5 for 3-4 years now, and it’s absolutely fantastic; I occasionally will use it in an underwater context (rockpools etc), but 99% of the time I use it on microscope mode for macro shots of insects, flowers, etc. About a month ago I decided to get the TG-6 as my 5 was getting a bit battered, slowing down a bit, which was understandable given how much I use it and the conditions I’ve put it through (still working fine though). What I found is that the TG-6 takes worse close-up shots! I was trying to take pics of a few insects, and I just couldn’t get as close to the subject as I normally would with my TG-5; all my close shots were blurry/crappy resolution. I took out my TG-5 which I had in my bag, photographed the exact same subjects, and had no issue at all.
One of my mates was in the same situation as me; used the TG-5 for a number of years and then recently bought the TG-6, and he had the exact same experience, i.e. the TG-6 seems to be a worse camera (at least for taking close-up shots).