In my opinion EBCs are superior to adjustable T pieces as they eliminate boost spiking and different boost levels under different loads (different gears). I ran a Turbosmart gated T piece for about 18 months before switching to an AVC-R three years ago.

My T piece was set up close to the turbo as is recommended but it would still spike slightly on a cold night (particularly in higher gears). There are no such issues with the AVC-R as it holds a constant boost level in all gears at all times.

It really depends on your budget. If things are tight buy a T piece and save for an EBC but be careful not to set the boost too high as you will see some spiking regardless of whether it is set up on a dyno or the road.

I am very happy with my AVC-R bu they are not as user friendly as the Turbosmart E-Boost and E-Boost2. I have heard nothing but good things about the Turbosmart EBC.
Regards Matty