As a tandem, the MR Explorer. I don't own one, but I paddle them all the time since several of my friends do. I should buy one someday.
As a solo, my Bell Wildfire - 14' long, 28" wide, 2.5" symmetrical rocker. A great river boat that handles lakes just fine. Not a lot of depth, so not a lot a freeboard when loaded, but also not a lot of boat sticking up to catch the wind on lakes. This is the Moose River Bow trip a few years ago - little bit if everything - mostly flatwater, some lakes, couple of portages, few easy rapids...
Typical load for me is two big bags - one in the bow one in the stern. Room behind the seat for my soft cooler and in the stern for my Dutch oven. A little room up front for whatever else I decide to bring. Two carries - I can get it down to one if I have to.
It's fine sitting or knelling. If you are poling it is not an option, but otherwise it is fast, efficient, carries plenty of gear, and (for me at least) more fun to paddle solo than my big tandem boat.
If you are paddling primarily on lakes you would probably want something a little longer without as much rocker - whatever today's version of the Bell Magic is.
You guys remember TommyC1? This goes back a ways, but when he decided to turn on the gas he left everyone, including the tandem boats, in the dust.