Yes, that's true. The key is "suits your goals" -- what's best for a drag racer is not best for a daily driver.

Nissan chose a GT25 turbo for some SR20DET, as the best combo of driveability, engine longevity, and power. For those goals, it is too big for a 1.4 liter. But for the goal of maximum full-throttle power, it may be just right, although laggy during normal driving. Still more power than a regular A14.

T25 is the bolt-on flange type. Most GT25 or GT28 turbos will bolt to a T25 flange.

GT25 indicates the turbine wheel diameter. There are low-flowing GT25 and high-flowing GT25. Depends on how it's made, and the compressor diameter. "GT" stands for Garrett Turbo, an OEM company for Nissan Silvia turbos. See http://www.turbobygarrett.com/turbobygarrett/garrett_nomenclature

So a smaller T25 turbo would be good for an A14. Or an even smaller Garrett T2, which was the stock turbo on a Nissan S12. For best driveability (least turbo lack, increased throttle response), fit a smaller turbo. For best full-throttle high RPM power, choose a larger turbo at the downside or more lag. Sikyne put a GT2860R on an stock A12 and made tremendous HP, but no report of how it drove in town traffic.