It is the cheap alternative for a durable center diff.
I've gone from a 2 spider to a welded center, back to a 2 spider, and back to a welded diff.
Driveability, hands down, the 2 spider is better. The 4 spider will offer the same driveability and offer the durability that most people will be after, although it will never be as strong as a welded diff.
With the welded diff, the axles click and the tires skip on tighter turns (parking lots, for example). I seem to be burning up tires a little faster than I did before as well.
The nice thing is that the car is more predictable with the welded center diff. At high power (550awhp+), the car torque steers the same way every time, on level ground, it slides the same way as well. Although I can't recall if I ever had the car turned up with the 2 spider... I've just been too worried about breaking it at. Even just launching the 2 spider a dozen times with the car at 440awhp, the spider gears were not in any condition to be put back in a transmission and be trusted to hold up.
If you have the money and aren't making 600hp, go with the 4 spider. Otherwise, I find the peace of mind in the welded diff worth the clicking axles and tire wear. I have yet to break an axle with the welded diff.
I do get audible drivetrain harmonics even with the sprung 6 puck similar to what I had when I had a twin disc, but it's only on decel and not as noisy as when I had the twin. I have a lot of solid and poly bushings which do not help this problem. It's not usually a problem for most people.