If you want simple, I would say TG-4.
For a very versatile system that can do a lot very well, the Rx100 with wet lenses for wide angle and macro is tough to beat for the money...
I like my tg-4 setup (it really is a nice simple system to start out with) but I suspect in the near future I might convince myself I "need" to upgrade to the rx100. It'll cost some money for the camera and housing but my uwl-04 can mount to a couple different housings for the rx100, so at least I can retain my wal and my ys-03, and probably add a second strobe and then have my tg-4 as a backup just in case for trips.
The 1" sensor of the rx100 vs 1/2.3" of the tg-4 sounds like a good upgrade. My local diving is deep and in lowish vis (30-40ft) and I just think the tiny sensor of the tg-4 is going to be a limitation in these conditions... dive report from this weekend with some shots with my tg-4 in deep low light water Destin diving (tg-4 content)
True. But, with a TG-4 or RX100, you have no choice of lenses....
I believe there are a few options for WAL for the rx100, and I know there are a couple for the tg-4. I'm not sure if there are multiple options for macro though.