Lots of points to discuss.
Turbolag.
Turbocruiser is right, his trucks has very little lag. However I have also driven other Safari's trucks and they did have some. It helps when the exhaust is done right so the turbo can spool up quicker.
I had a boost gauge on mey sc'ed truck and it hardly ever boosts off-road. I also have a friend with a turbo that wheels with us. Never had it make power so fast that it jumps over stuff. We typicall use powerbraking when wheeling in any case. Spool the motor up, control the forward progress with the brake pedal. Makes it easier when wheeling the auto and you don't have low enough gears.
Underhood temps.
In all the cases we have done, the sc was worse for underhood temps. The sc blocks a lot of the airflow that cools the exhaust manifold. The turbo trucks we have done was not as bad. Yes, the turbo itself does run hot, but the underhood temps are better.
Install
10+ hours, depending on what else is done. I would venture that there are very little 80's out there currently that you can just slap the sc on and not worry. I have bought two 93's with melted pistons due to sc installs where no additional care was take.
Unichip,
we do not install the chip. We had two cases where the unichip failed due to ambient temprature. The truck just dies. The unichip only adds/remove timing and fuel. It can not deliver more fuel than the system can supply. We have never seen a 97 truck run lean with the turbo. Also, the chip should be tuned on a 4 wheel dyno that can apply loads. Not very many of them out there. In addition it is tuned for your locations, ie, altitute etc etc. Doesn't really work in CO where we go from 5kft to 13kft.
Yes, when the Ausies do it, it seems to work, and they get good results. I think mostly they are tuned to not make the truck run to rich.
Mileage
, the turbo has the edge in terms of effeciency, but I would not say you gain anything. If you want to move a brick faster, it takes more energy.
Reliability,
I think both are about the same. The turbo is a more complex install, but if done right, no reason it would not be as good as sc. Yes, you have to cool down the turbo when it was run hot, but turbo timers take care of it. Also if you have a sc, also a good idea to let the engine cool down when run hot. Heatsoak is a bad thing all round.
Parts,
not sure on that. Been waiting for some time on info on a nose cone rebuild kit from TRD (hey Cdan, you need to kick their butts a little)

The worst thing on the Safari is the casting. If that cracks, you might have to do some custom work and retrofit a regular garret turbo. Has been done before.
Availabilty, yes there the sc has the edge. Turbocruiser, who is going to bring 50 kits in? Would like to speek to them.