I did not think 17" LCD monitors with LED backlights were actually ever manufactured, except maybe for custom industrial applications . Typically, older LCD monitors use CCFLs , not LEDs .
Are you looking to buy a new 16:9 or 16:10 or used 4:3 (older) monitor ?
If you are looking to buy a new 16:9 or 16:10 monitor .
a) A VGA input is essential unless you plan on using a DVI equipped video card or plan on using a VGA to HDMI scan converter or scaler .
b) Unless you don't mind 4:3 content stretched to 16:9 , an aspect ratio option is useful, an option to force 4:3 mode is even better .
Caveat : even with an aspect ratio option, most modern monitors will still stretch DOS modes to 16:9. You really need a 4:3 mode to avoid the stretching .
If you are looking to buy an older used 4:3 one .
a) VGA input is a given, DVI is not . If you need DVI make sure the monitor has it .
b) Make sure brightness is good. LCD monitor backlights get dimmer as they are used . Replacing backlights is a PITA .
c) Make sure it supports the resolutions you want to use (DOS modes are a given, but 17" monitors are typically 1024x768 native, though they will accept lower resolution and scale to their native resolution)
d) 19" monitors are typically 5:4, not 4:3 , so 4:3 modes (DOS and Windows) will either be slightly stretched vertically or have black horizontal bars of unused space on the screen .
EDIT : This is off the top of my head and not guaranteed to be exhaustive .
EDIT2 : Monitors will usually have not trouble accepting DOS modes which are 70Hz over VGA . Some will actually display 70Hz, other will convert to 60Hz before displaying . The degree to which this is noticeable varies from person to person and likely also with implementation . This is rarely documented . Over DVI, everything is usually forced to 60Hz by the video card. There are way around this, but they require extra hardware and will likely only work with modern monitors that can handle more than 60Hz over DVI .
