I'll have to say Zenith in terms of reliabilty and picture quality. At the moment I only have 3 Zenith sets, and they are all B&W. One is a 1972 Zenith 4 tube hybrid set I got from maxm (all handwired except the video IF PCB). That TV gets beautiful picture, as well as surviving some shipping damage.

I had a Zenith System 3 set that I got last Winter that sat out in single digit weather after a rain from a warm spell earlier that week. Got it home with ice in the TV. After drying out for a day in front of a space heater, it worked perfectly with no adjustments on it. However, I thought it said 1981 for a date, while it turns out it was from late 1984. A TV has to be older than I am to be in my collection, so I kind of lost interest in it and eventually got rid of it to make more room for some more old TVs...

Though many will say GE TVs are junk, I have a few of them, and they work extremely well, with very little work done to them. One is a 1977 GE with a modular chassis. It sat outside in the rain for about 1 and a half weeks. I picked it up anyhow one night coming home from work. After drying it out, I plugged it in and it worked perfectly as is. The focus is razor sharp on it, and an extremely bright picture tube. It looks like it has had a lot of hours on it, but doesn't show it.

I don't have enough experience with RCA to comment on. I only have two, and the one I bought it 2 months ago while I was in Erie, PA visiting some friends at the SA. This was our first TV from when my parents got married. It is an RCA XL-100 from 1981. Nothing special, but had to have it simply because I remember watching TV all the time on it when I was little. That TV must have had a crap load of hours on it... I readjusted the screen, bias and drive voltages on it. The screen is up pretty high, both drives are at minimum to get the proper greyscale. If you crank the brightness, the all 3 guns start to bleed, especially the red. So the tube is a bit weak, but still bright.
I have a 1974 16" B&W tube RCA with a solid state remote control circuit. Definately not built as well as the Zenith I mentioned, and needs some work.

That's all I have to comment on right now