In a Nutshell then.............

Hybrid Turbo - Is exactly the same size as the standard GT25 Turbo in your car. Most have GT28 Internals so are capable of providing good power returns. No adaptions are needed for a Hybrid, so your CAT will fit it come MOT time.
However, they spool up very quickly and give you a massive shunt at low revs which can cause the car to feel unstable and skittish. Hybrid's are typically run direct off the Actuator but over time the spring will wear and boost will drop slightly, meaning adjustments.
Price wise - Somewhere around £700.

GT28 Turbo - Is simply a bigger all round Turbo Unit. It has strong internals and provides massive power, but brings with it slight Turbo Lag, which is lovely coz the Torque will drag you along until BANG, it comes on boost. Alex's car has one of these and is pushing 416bhp @ the Fly.
A Hybrid will NEVER reach that kind of horsepower coz its not strong enough.
GT28's need a specific De-Cat to pair it with the manifold & Exhaust.
There is NO CAT for this turbo. You have to De-Cat.
GT28 needs a Boost Controller to operate the best from it.

If you want big power (over 380 bhp) then GT28 is the one to have.
Price Wise (Via SCC) - £1895 Turbo fitted and £500 Blitz boost Controller.

Choice is yours.