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Factors I can think of:

1. Bigger mirror = better. Enclosing a mirror requires mass and volume, limiting mirror size.

2. The L2 orbit is unstable. Far less risk of being hit by debris than low Earth orbit.

3. Webb's sun shield blocks the primary light pollution angle. Hubble would need more protection from all angles due to the Sun, Earth, and Moon.

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Did not realize the light pollution angle, that's a major one.

I also had no idea L2 was unstable and found a little discussion on it. https://space.stackexchange.com/questions/284/why-should-the...

Here is a good video about the stability of L1 - L5 points

https://youtu.be/7PHvDj4TDfM

4. Any variations in temperature in the mirror array affect geometry/optics

I was just reading that after L2 insertion it's going to take five months to get everything cooled off and aligned properly. Amazing.

Cooldown has already started with the deploying of the sunshield from it's launch position, even before it is unfolded fully and stacked properly the delta is already a whopping 60 degrees Celsius across a bit over two meters.

Maybe we will get lucky and find out something like this announcement.

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