[wayner]

Aside from the fact that multi-way adjustable damping is more common with coil overs
(and adjustable spring perches make ride height adjustments easy as mentioned)

The main reason for coil overs is that that take up less space.
A coil-over spring and a torsion rod are the same thing (a spring)

When the 1973 factory race team needed to go to even larger torsion bars, they found space an issue so fitted coil overs.

With the spiders that Pensky and others used in American lemans etc. just a few years ago, they employed torsion bars and not coil overs.

There is nothing inherently better about a coil over spring than a torsion bar unless you are changing the size of the spring at the same time.

Some people even say that since the torsion bar is mounted lower on teh chassis it is better since it doesn't transmit the load up high on the chasis.

If you are looking for better handling, if it were me I'd look at what characteristics you want to change.

If you aren't looking at changing the shocks or spring sizes, then i'd just go for whatever adjustments and improvements you need. If your are changing shock valving, getting more adjustability or bigger bars dont fit then getting the coil over may be a good choice for future tuning even if you keep the same spring size, but not because the springs are better than the bars.

When most people say the coil overs handle better, its because along with those simple bolt on parts, they received a lot of other improvements that came as part of the package. It wasn't from the coil part of the coil-over shock unless we are also talking heavier springs.