I'm researching turbo upgrades at the moment so I'll summarise what I've found already:
Hybrid = (17/22 or GT1749VC) Straight swap with a standard setup as this turbo is a GT1749VB (PD150/PD160) with upgraded internals which see max power around 220bhp on stock injectors and turbo pretty much maxed out. Readily available to bolt on power upgrades. For full potential you'll need a FMIC, uprated clutch and remap.
GTB1756VK = (2.7/3.0tdi - third generation VNT) More work involved. Custom Manifold (or welded), downpipe flanges and turbo outlet pipe. Will see around 220-230bhp on stock injectors but turbo delivering more boost longer over rev range. Spools similar to stock turbo so suited to daily driving well. For full potential you'll need a FMIC, uprated clutch and remap.
GTB2260VK = Same work as the GTB1756VK with install, however will see
280-300bhp with Firad 80%+ Noozles etc... This route isn't cheap and you'll need SMF as DMF won't last long and LSD to keep the power on the ground. Also spool times are a little longer so power range is higher on the rev range. For full potential you'll need a FMIC, uprated clutch, SMF, injectors and remap.
GTB2056VKLR - (Ballbearing Water Coooled - Mercedes) Best compromise for both spool and boost. Sits between GTB2260 and GTB1756VK but rare to get hold of with vacuum conversion.