Viewing Preference?

For those with a 16:9 monitor... 1 - when you view a 4:3 source for an extended time (i.e. typical movie length 2 hours) do you prferer it stretched or normal size with the side bars? 2 - if you use 4:3, is it better to avoid burn in to use gray or black side bars?
Also, thanks to this forum, I found out how to set the output of my Comcast HD box.
I have a plasma and although leary about burn-in, I use the gray bars for watching 4:3 source. Thankfully, that is not a lot since there is a lot more 16:9 HD content on now.
4:3 with gray bars. When I researched this quite a while ago, I found out it is better for the projection tubes to run gray bars than black.
For my Mits. crt,they say 10% of your viewing with with bars. My crt Pioneer tv had burn-in marks when I dumped it.These were noticable on a solid white or blue screen and showed up as brown vertical marks. So I now watch most everything;stretched.
I view everything in OAR (original aspect ratio); e.g., I view 4:3 in 4:3.

For cable sources, I use the darkest side bars I can in my HD STB, but I would describe them as dark gray rather than black. If black were an option, I would use that.

IIRC, 4:3 DVD sources have black side bars.

One of the reasons I bought a microdisplay based RPTV is to view everything in OAR since they do not suffer from burn-in, and I hate stretched images.

I run my Hitachi RPTV (51F710) in stretch (expanded) mode or use gray bars. The Hitachi has a particularly good stretch mode...