You can get the Night Pearl PR2 lamp from Sinotone International in San Francisco 650-583-8306. I've ordered from them a couple of times and service has been prompt. Unfortunatly they are on vacation until June 26, according to the recording I got when I tried to place my latest order. Based upon a very small sample of Sinotone lamps (3) and Tech Associates lamps (2) you could maybe say that the white LEDs in the Versa-lux lamps were graded for more uniformity in color rank. But maybe I just got lucky with my Tech-Assoc. order.
Performance wise, other than the minor color differences, there isn't any difference in performance between the two brands.
How happy you will be with these lamps in your lights has a LOT to do with the reflector. Some lights give a tiny hotspot that will light stuff across the street, but is pretty useless for close work, some lights, especially those with faceted reflectors, will give a better beam for close work. If your light gives a crappy, uneven, bullseyed, etc., beam with the regular incandescent lamp, the LED bulb may not change that. You can try adjusting focus in some nonfocusable lights by using custom cut "washers" to shim the bulb lower in the reflector. HTH