the t3 and t3/t4 share the same exhaust turbine side, right? ...it's just the hybrid has a larger compressor, correct? if that's true, let me quote a paragraph from 'maximum boost':

"Larger or smaller compressors do not have a huge effect on turbo lag or boost threshold. The compressor wheel is the lightest rotating part of the turbo; hence, it's contribution to the total inertia of the rotating assembly is fairly low. Boost threshold is mostly a function of the turbo's speed, which is controlled by the turbine." - Corky Bell.

to me that means that if the exhaust turbine is properly matched to the displacement of the engine, then lag won't be a factor with either choice. and of course more power being available from the hybrid turbo.