The handheld lcd panel is actually ok to use. For external display, I am using a dock and running the hdmi out to the dvi port on my monitor because none of my displayport adapters work on it, but I have since learned why and which ones will work so I might buy another adapter to try the vga port. I don't use the thing much to be honest but it's not because of discomfort, just because I'm not in a gaming mood at the moment.
The oled one is problematic because people who say they are fine with other oleds complained about this one. Also, people measured it with instruments like the opple and others and saw that there are issues with it. Valve said they aren't going to fix/change it (probably can't), so it would be better to wait till the next generation if you want an oled handheld panel. Or I guess, get an oled external monitor that works for you and use that with the lcd panel one.