I would say there's three things to look for: first, as already mentioned, the color: look for "warm white" or if it's listed in Kelvins, something in the 3K to 4K range, higher than that starts to get bluish. Second, look for light output: a standard 921 bulb has an output around 250 lumens, so if you want something bright as the stock, shoot for something in that range. Lastly, look for a LED that emits light in all directions. Some of the cheaper 921 replacement LEDs are flat panel or "ping pong paddle" shaped, but they only throw the light "down," not "out" (in an overhead application, for instance.) Most of the overhead fixtures are designed to have light shine/reflect out to the sides, but it has to be that kind of bulb or LED. Good luck!
2015 XLR Hyperlite 30HFS5 (mods being performed regularly)
2009 Salem LA 292fkds (gone)
Nights- ('12)23 ('13)23 ('14)15 ('15)31 ('16)25
2014 Harley Davidson FLHX (XLR cargo)
2014 VW Jetta TDI (diesel sipper, camping support vehicle)
2011 Ram 2500 CC 4X4 CTD, B&W Companion (toy hauler hauler)