Just because a screen is widescreen doesn't mean it has less vertical resolution at all. It MIGHT... But just because you have a 19" 4:3 doesn't mean it can do 1600x1200 any more than any other monitor. My 24" dell does 1920x1200. I would hardly call that "reduced height". 16:10 is just that... 16:10. 4:3 is 4:3... More or less pixels depends on how good the monitor is, not whether it's widescreen or not.
Of course... but:
The *typical* native resolution of a 19" widescreen is 1440x900. a typical 4:3 screen is 1280x1024. The majority of LCD's don't give you a higher resolution than that unless you are looking at 20.1" and above.
Anyway, 1440x900 vs. 1280x1024, is 1.29Mpixel vs. 1.31MPixel. But the real difference is in square inches though: a 19" 4:3 screen give you 173.28 square inches of display, while a 19" widescreen gives you 154.27 square inches.
The widescreen gives you slightly smaller pixels, but you definitely have a larger surface area on a 4:3 screen. (Remember pythagoras? A^2*B^2=C^2 and all that)