The T4 and the 3F do share similarities in the topology of the output stage, but the implementation is very different. The T4 is high voltage, low current with a step down transformer (and a DC blocking capacitor) while the 3F is high current, low voltage and is DC coupled. (The 3 - as opposed to the 3F - uses an output transformer, but no DC blocking cap.)
The T4 has a single ended input with a tube LTP stage for gain and splitting. The 3F has an input transformer for gain and splitting.
3F is generally the better Focal option, but it is for balanced phones only.