Pro's Its cheap, and pretty strong if welded by a competent welder.
Cons Wears out tires quicker, puts more stress on axle bearings when turning, constantly chirps tires when turning, can make the front end "scrubb or push through" while turning in some situations.
What are your plans for this car? Ive had a S10 that I put a minispool in first (locks the diff full time) and after a few months started to hate it. Didnt take long to realize i wasted cash I could have put towards a locker. My old 78 Chevy 3/4 ton 4x4, I had a nieghbor that owned a welding shop weld up the rear diff. It worked great, but then again, I only drove it on the road to get to and from my offroad wheeling locations. I would save up and get a Ford Racing Trac LOC. You can pick up the 28 spline version for $199.00 new.
Your best bet would be check the rulebooks for the class you plan on running in. Welded spidergears are frowned upon in most forms of competition. When failure occurs, the spider gears shatter. Right inboard of the spider gears are the axle c clips that hold the axle in.
Biggest con....when it goes..... it takes everything with it..... buy a full spool for like 120 and c clip alums for 180
Pro its cheap.... and like said if done by pro a welder who knows what the metal is and the proper filler etc.
As long as you don't drag race I think it will be fine. Only seen welded gears fail 3x.... twice while drag racing on. Prepped surface with drag radials and once on a 350 swapped jeep who was climb bounced and came back down and POP!!! Funniest part was dif fluid got into the lake and game and fish called the fire dept.... so if there is a sudden shock they could break. Drifting I don't think so...