14 = PVS14 which is a case style, the image tube inside is what makes the image.
Different companies make the image tubes, like ITT make the pinnacle and Everest tubes, L3 makes the chrome (white phosphor tube) and regular L3 tubes, Photonis makes XR-4 XR-5 and various other models. Shades of green is the most common color, some are darker green others are yellowish, white phosphor is black and whiteish, L3 calls thier version chrome
The higher the signal to noise ratio the better contrast and less noise especially in low light, the L3 tubes have been really good lately +30 s/n ratio and higher ( over 30 s/n in the past from any MFG was hand picked diamond +$4000 unit). ITT tubes +28 s/n is common with the pinnacle line, I have 2 that are 27.8 and 27.7 s/n 64 lp/mm and 72 lp/mm paid under $2650.00 ea with 5yr warranty.
Other factors like lines per millimeter or (sharpness). Most tubes min specs are 64 lp/mm some are as high as 84 lp/mm but much much less common.
New tubes usually have a spec sheet with them that show the performance. The generic all in one number is the Figure of merit which is the lp/mm times the s/n ratio. FOM numbers above 1400 for ground and 1600 for aviation use are not exportable, unless proper paperwork is completed.
