Or a 2-way. IIRC
Spools are the BEST way to go. For any car.
For the street, or lots of turns…very very bad. Axles shoot out. Chew the shit outta your tires, wheel/axle bearing. All kinds:)
Every tried pushing a full drag car with a spool? Next to impossible to move by your self. That’s straight, never mind turning! HA
so… are you circuiting the car ? drift or drag ? because like peter said, if you want the slowest time weld your diff, from my experiance i think a welded diff takes a little time to adjust your drifting to, as it does give a little understeer, its almost as if the car wants to start the corner a little later than you would, but anyways if your dragging welded is perfect, depending on the power you have, but peter has around 300 and hasnt had any problems for 2 years ? and hes not gental lol
my buddy has a welded diff in his 91 240.
Wheels skip/hop while turning at slow speeds. noisey.
but when used for the whole purpose of having a welded diff its insane! 
very fun.
Also the inevibility (sp?) of the welds breaking destroying your diff 
i had a diff blow on me already, no biggy.
drag for sure but i kinda want to focus more on circuit and drifting this yr
2way is actually noiser.
Whenever I did sharp turns or esp. reversing, sounded like someone took a sledge hammer to the rear subframe.
JUST got a welded installed and so much quieter than an actual 2way.
Only thing I don’t like about a welded is in reverse, if the tires are too grippy, it literally stops the car whereas a 2way would just clunk.
Yea can’t be Elon. The Elon I know would buy his welded diff from ebay, lol.