My vote is for the OTG. I fire up my 22" Weber Kettles all the time, even for small stuff like just a steak and potato.
Typically, the routine is like this. It is quick, simple, and all of the words to describe it make is seem far more complex and difficult than it really is.
1. I put a couple wads of paper under my Weber chimney (it's bigger than the average chimney) and fill it just under halfway with new charcoal, then top off with whatever is left behind in the unit from last time. If needed, I top off with new charcoal but this almost always fills the unit between the new and used stuff.
2. I light the paper, then turn the blades in the One Touch system to clean out the ash leftover from the previous cook.
3. I go inside to prep something (or finish prep)...season meat, whatever. I just need about 10 minutes to get that chimney fired up.
4. I dump the lit coals on one half of the unit and use a fureplace shovel to arrange the coals on that half evenly, then put the grate on to heat it up and put the lid on (vents open of course).
5. I go back inside to bring all the stuff out for cooking. By that point I brush the grates to make sure they are clean, rotating them to get both sides.
7. Shut down the intakes and exhaust as soon as the meat is pulled.
Wow. That's it. Pretty much anything you cook on those things (save for longer smoking sessions) follow those exact same rules almost to the letter.
I have cooked just a single steak/burger/chop/whatever for lunch (search for my Q-Talk threads, many are jsut what I had for lunch), all the way to feeding the family on that thing complete with sides, with the same setup every time. The trick is simply having methods and timings for moving items from the hot side to the cool side. This isn't an issue for smaller cooks like you are looknig for.
So, in a nutshell, I see no reason to get a smaller cooker if your goal is smaller amounts of food to cook.
If portability is a factor, well, then that's a whole different story and I would probably suggest the rectangular Weber in that case.