A couple of more points, the lamps beam varies in angles, the 4 Watt MR16 LED Bulb - Wide Beam Angle (50 Watt Replacement) I linked to are 120 degree some are a lot narrower.
The colour you finish the inside of your van will also determine the amount of lighting you need, black or a simliar dark colour will take more lighting than a white or pastel colour interior.
The colour of lamps are to personal taste. Fluorescent lamps, warm white, cool white, daylight are all different tempretures on the Kelvin scale ranging from 2.7k to 6.4k. The SAD lights are typically around the 5.5-6.4k.
I've changed all the lamps over in the house to 6.4k lamps, a very bright white light, mimicing daylight, takes a day or so to get used to it but a much better light, hate it when I go into a house lit by the yellow lights 2.7k.
Leds vary in colour as well, no surprise I go for those higher up the kelvin scale. Look out for the different types of Led. CREE which when switched off are a yellow square
(as can be seen here) or the more coventional bell shape
seen here.
The CREE Leds are the best giving out much more light.
Cut n Pasted
What type of light quality can I expect with LED lights? You should be satisfied with the light quality coming from any light—LED or otherwise. The best way to ensure this is to know what color light you want and how to ask for it. If you want warm light, look for lighting that is close to 2700K. If you want a more neutral light, look for something closer to 3500K and if you want a cooler light, look for 5000K or more. But that’s not all… You also need to be aware of color rendering.
The ability to make colors look true – that is to have a tomato look like a tomato – is called color rendering. The color rendering index (CRI) characterizes light sources in view of their ability to produce “natural light” and can be between 0 and 100. The closer an LED light comes to 100 on the color rendering index (CRI), the more naturally colors are rendered, and the light is perceived as more pleasant. The CRI of fluorescent tubes is often around 72. Cree LED lighting fixtures have a CRI of between 92 and 94.