I ran a spooled rearend on the street for 3 years. It is doable but the tire wear is insane. I recently switched to a Detroit locker in the rear axle and I was shocked at how much better it acts on the street then the spool did.
If you are building an offroad truck that sees more dirt then street then a spool is fine. But if you run the street alot you will get tired of the chirping around corners and the rapid tire wear issue.
Offroad you will not really notice a difference. A locker and a spool are going to provide the same amount of traction. A spooled front axle can be a PITA offroad as it will make it harder to steer the truck.
As far as steering with a spooled rear on the street your turning radius will increase a fair amount. A spool is not real user friendly on the street if you DD the truck. It can definitly be done though. Like I mentioned I did it for 3 years on the street.
The only bonus the the spool is that they are cheap, strong, and they have a very predictable road manner. The locker can be a little quirkie with the locking and unlocking especially in the ice, snow, and rain.
Harley