My thoughts exactly.
The negative comments youve heard about welding the spiders are probably just the bad street manners. The tires are gonna chirp around every turn you make....drastically increasing tire wear. If you really want a spool....save the $90 and just weld it. It accomplishes the same thing.
If your driving on the street, I would highly advise against either option. Instead of spending $90 on a spool, spend $200 on a lockright and you will be much happier imho. But if your really inclined to have a differential that wont unlock at all....spend $2 on some welding rods (or spend $20 for a welding shop) to just weld it up.
-Harrison