Twin-charge is the way to go on the street. For the track, turbo is probably better, although zzp built a twin-charge car that ran 9.9, so I think we can rule out the assumption that the supercharger is somehow creating a limit for the turbo.
The biggest advantages to twin-charging is that the turbo can be sized much larger to create better top-end boosting while still maintaining plenty of low-end torque with zero lag. This is most advantageous on the street where you are driving in many different rpm ranges and want instant power. I really like the feeling of the instant power in every gear and speed. Swapping smaller pulleys on a twin-charge setup creates even more street power, but sacrifices the top-end limits because of the stack effect.
Twin-charging will create more heat, as the boost still tends to "stack" even after the bypass is active. This stacking is what gets the boost up to full much faster, but the additional heat must be dealt with, which is why it is recommended to have a twin-intercooler setup installed.
There are not very many twin-charge setups, so I don't know who started the rumor that it is difficult to tune. It is no more difficult, or even different, then tuning a larger turbo-only setup. Boost comes in earlier, so PE vs. TPS is adjusted to handle that, but other than that, it is basics.