Those are two very different windows...
Anderson uses pine, which paints well but does not stain well
Anderson are also vinyl clad on the exterior and the choices for color cladding are limited
Anderson typically has a shorter lead time for delivery
Typically Anderson is less expensive but a lot depends on the specific factors such as operation, size etc

Pella is pretty high end.

Usually people who are considering Anderson would not be considering Pella and vice versa

Bring your plans to both and get pricing on both

Ask about materials used, delivery time, as well as exterior cladding options

Also consider whether they are willing to customize the windows if needed

Good luck!!

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