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Standard H4 (60/55W) is an economical quality replacement for the stock bulb in the early Vanagons. In Europe T3s were also sold with round headlights at a later date and rectangular lights also used H4 bulbs.
H4 blue has the same power consumption as the standard on but it offers a whiter light due to its blue color tint.
The 9003 Vision Plus is also an H4 bulb offering 60% better light according to the manufacturer. It is definitely a better light but we are not sure how the 60% are measured. Their power consumption remains the same as standard bulbs.
The 9004 standard is a straight and economical replacement of your stock outer headlight bulb.
The 9004 Vision Plus bulb is an upgrade worth considering as the stock rectangular headlights do not provide great illumination to start with.
If you want to get serious with an upgrade the Xenon/Halogen Crystal Vision Plus 9004CVP replacement bulbs are for you. They provide a bright whiter light.